Wednesday wildflower: Veronica hederifolia

Last week I was at Lincoln, near Christchurch, working in the herbarium at Landcare Research.  I was checking my descriptions and identifying specimens towards my Veronica treatment for the new on line Flora of New Zealand, the eFlora.

Veronica hederifolia growing at the foot of an oak tree in the Liffey Domain, Lincoln.

One of the introduced species (there are about 20 of them) that I hadn't yet seen grows right there in Lincoln, so it seemed a good opportunity for a field trip to collect and photograph it.  Veronica hederifolia plants are soft annual herbs that creep along the ground.  Their flowers appear to be solitary in the axils of the upper leaves, but that depends on an interpretation.  Leaves that don't produce flowers are opposite, but there's a shift to alternate leaves, each of which has a flower in its axil.  It's probably reasonable as an alternative interpretation to consider this to be the initiation of a terminal inflorescence. In any case the leaf form doesn't change, whereas in many Veronica the flowers are produced in the axils of much smaller and simpler leaves, which are designated as bracts.

Veronica hederifolia growth form.

V. hederifolia has been growing there in Lincoln along the banks of the L2 river for over 50 years.  The botanist who collected it last—in 1985—was able to tell me exactly where to look, and there it was. There's one other collection in Landcare's herbarium, from St Mary's College grounds in Christchurch, and the Flora refers to other verified locations in Hawke's Bay, Manawatu, and Southland.

Although V. hederifolia looks a bit like V. persica in the way it grows, there are a lot of clear differences.  The leaf shape for one, but also the flowers are smaller, and the anthers are held right against the stigma so it self-pollinates, in spite of producing lots of nectar.  The fruits of V. hederifolia are hairless, circular, and barely notched, whereas fruits of V. persica are hairy along the edges of two widely diverging lobes.

Veronica hederifolia flower.

The calyx lobes are folded length-wise and have long hairs along their edges.

Veronica hederifolia, calyx.

I've taken a few small plants to try to grow it on at home, but annuals can be hard to transplant, so I'm hoping fruits and seeds will be ready when I go back to Lincoln next month.  Then I'll be able to finish my description by describing fruits and seeds and bring home some seeds to grow in the garden.

Wednesday wildflower: Cape weed

Here's something to watch for if you like foraging for wild food: be very careful about misidentifications.  I remember visiting someone in Christchurch once who was carefully transplanting wild hemlock (this one) seedlings into her herb garden, thinking they were angelica.  Well, I shouldn't be smug about that, because yesterday I made a mistake that could have had nasty consequences if I'd been foraging and if the mistake had been in the reverse direction, but I like to think I wouldn't have made it if I'd had a fresh plant or a dried specimen, rather than a photo, to identify.

It was on the Naturewatch website, and someone had posted a photo with a request for identification.  I thought it looked like puha (Sonchus oleraceus), but then I changed my mind and identified it as Cape weed, Arctotheca calendula.  The great thing about Naturewatch is that the identifications are crowd-sourced, and others quickly challenged my identification and convinced me, with evidence, that I was wrong.  The plant was indeed puha (Sonchus oleraceus).  (It's a bit embarrassing, because I wrote the Flora of New Zealand treatment for both these plants.)

So yesterday, I went looking for some fresh material.  Here are the upper surfaces of the leaves:

Cape weed (left) and puha, upper surfaces (scale=1cm)

And here are the lower surfaces.

Cape weed (left) and puha, lower surfaces (scale=1cm)

The Cape weed has more leaflets, a rounded, rather than triangular terminal leaflet, bristly hairs on the upper surface and a dense silvery mat of hairs below (puha leaves are hairless except for bristles at the tips of the teeth on the upper leaves).  Cape weed's leaf stalk is also bristly compared to the smooth puha.

Of course, it'd be hard to confuse them in flower, but early growth is often the time when foragers collect, because some plants get bitter when they run to flower.

Cape weed (left) and puha in flower.

Cape weed is poisonous, but not very, whereas puha is edible.  Check out Johanna Knox's foraging website for information, and always be sure you identify your target.

The moral of the story is that identifying plants from photos can be difficult.  Often the diagnostic characteristics can't be seen and sometimes the colours recorded in a photo don't look the same as in life.  Plant taxonomists (specialists in the classification, naming, identification, and evolution of plants) often refuse to identify photos, but I believe that so long as people understand the pitfalls it's worth having a try.  I really like the Naturewatch site, because it's self-correcting, democratic (everyone can have a go), and we all learn something from participating.

Wednesday wildflower: old man's beard.

“Old man’s beard must go,” said the not-so-young bearded botanist David Bellamy some years ago on TV, and we all knew this was a serious weed that threatened to smother our native forests.  Since then, it’s not as common as it used to be.  The efforts of the Department of Conservation, local and regional councils, community groups, and individual landowners have largely seen off the worst infestations in many places.  But around Wellington city, and probably many other places, there are little pockets of old man’s beard everywhere.  My guess is it’s waiting for our vigilance to let up and it’ll be back with a vengeance.

Old man's beard fruits, Northland, Wellington.

Old man’s beard is called traveller’s joy in England, which goes to show that one country’s wildflower is often another’s weed.  The local name refers to the fluffy white plumes on the seeds.  More accurately (with my pedantic botanist’s hat on) these aren’t seeds but fruits, each bearing a single seed inside a loose-fitting fruit wall.  The flower, like many in the buttercup family, has multiple separate pistils, each with its own ovary, style and stigma.  After pollination, the pistils from a flower mature into a cluster of separate 1-seeded fruits, each with the fluffy remains of the style to form a plume that assists in wind dispersal.

One of the practical problems with a public eradication campaign is that people need to be able to recognise the target weed, and not try to eradicate look-alikes.  Many people worry that they might be pulling up one of the native Clematis instead, so I thought this week a few notes about these plants might be useful.

First, old man’s beard (Clematis vitalba) is one of just two species in New Zealand with once-pinnate leaves; they have a central axis with a terminal leaflet and two pairs of lateral leaflets.  The other species that’s characterised by once-pinnate leaves is C. maximowiciana, but its leaves are more leathery than the leaves of old man’s beard; also it has larger flowers, 30–50 mm diameter.  Most of the other species have three leaflets although these can be quite finely divided.  Two species, C. tangutica (yellow flowers) and C. flammula (white flowers), have twice-pinnate leaves (the pinnae [leaflets] are themselves pinnately divided).  The native C. afoliata has no leaves at all, just the leaf stalks that twine around supporting shrubs’ stems.

Old man's beard flowers, Kakariki, Manawatu.  They are mostly 12–25 mm diameter

Secondly, the introduced species mostly have 4 sepals in each flower, but many (not all) of the native ones have six.  All the introduced Clematis have hermaphrodite flowers (with functional stamens and pistils) whereas the natives all have unisexual flowers on separate plants (flowers have either stamens or pistils, but never both).

Clematis forsteri, a native species.  Pale yellow male flowers with 6 sepals.  If you see these, don't just look, sniff too: many are sweetly scented.

Most of the native Clematis flower in the springtime or even late winter (some plants of C. forsteri are in flower now in late July).  Old man’s beard is a summer-flowering plant, mostly from December to May.

Clematis paniculata, another native species, male flowers.

Old man's beard flowers are greenish white.  Most natives have pale or greenish yellow flowers, although the large (and unisexual) flowers of C. paniculata are pure white, C. marata and C. marmoraria are white or greenish, and C. marata quadribracteolata (corrected 4 September 2013) brown or purplish brown.  Finally, the introduced Clematis are all deciduous whereas the natives are all evergreen (except poor C. afoliata, which hasn’t got leaves to lose).

Old man's beard still must go, but let's hope no native Clematis get pulled out instead by well-meaning weed-busters.  The Flora treatment for their identification is on line at Landcare Research's website and you can find pictures identified by botanists at the Naturewatch site..

Wednesday Wildflower: Brazilian pepper tree

I've been wondering about some trees in Sunnynook Park every time I visit Auckland.  From the shape of their leaves and their panicles of small flowers I had assumed they're something in the Cunoniaceae. But I should have been more curious and looked more closely, because these leaves are alternate, whereas Cunoniaceae have opposite leaves with interpetiolar stipules.

Schinus terebinthifolius, a flowering branchlet from a female tree.

This week I was there again and saw one of the trees had little round pinkish fruits, and I realised this is Schinus terebinthifolius.  I knew S. molle, which has more graceful hanging leaves, and I knew the fruits of S. terebinthifolius are the pink peppercorns you sometimes see mixed with black peppercorns (Piper nigrum) in pepper grinders. (Pink pepper, confusingly, is made with true black peppercorns, using newly-ripened berries and treating them with brine and vinegar, described by McGee, 2004.)

It's becoming a bit of a problem weed in New Zealand and worrying some weed experts.  Back in 1988, Flora of New Zealand Vol. 4 didn't record it as naturalised (Webb et al. 1988), but now it seems to be establishing.  It's a major weed in many warmer countries.  The trees in Sunnynook Park don't seem to be spreading, although there appear to be suckers coming up from the roots.  Most of the trees there are male, but I did spot a couple of females.

It seems a lot of our new weeds are woody, and many are bird-dispersed.  I wonder how many originate from more tropical climates and owe their success here to climate change.

The Flora says it has 5–9 leaflets.  The leaf I randomly chose to photograph had 11:

Schinus terebinthifolius leaf

That doesn't mean the identification is wrong.  Many characteristics of plants are more variable than the descriptions cover, partly because the descriptions are based on a smallish sample that doesn't allow for the odd extreme.

Pink pepper is in the family Anacardiaceae, the same family as mango, cashew, and poison ivy; some people are very allergic to this family.  According to McGee (2004) it owes its peppery flavour to cardanol, an irritating phenolic compound.

References.

McGee, H. 2004.  On food and cooking, the science and lore of the kitchen. (Revised edition), Scribner.

Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. 1988.  Flora of New Zealand Vol. 4.  Botany Division, DSIR.

Experimental taxonomy at home.

Ernst Mayr pioneered the biological species concept, an idea that brought taxonomy of species into line with population genetics and evolution.  The idea is that a species is defined by the genetic relationships among its members; they’re all part of one big potentially-interbreeding population.  In Linnaeus’s day people sought to classify species based on what they looked like, rather than who they could breed with.

Using appearance is a pretty good proxy for the ability to interbreed, and much of the time it’s what taxonomists still do, simply because doing the breeding experiments or measuring genetic relationships among individuals is just too time-consuming.

But there are two classes of concerns that arise.

On one hand, individuals belonging to the same species can look very different.

Sometimes juveniles are hugely different from adults, like caterpillar and butterfly, elva and eel, or juvenile vs adult lancewood.  In a New Zealand plant example, Jim Le Comte and Colin Webb (Le Comte & Webb 1981) showed experimentally that the speargrass Aciphylla townsonii is actually the juvenile form of A. hookeri.  Different juveniles seem to be a feature of New Zealand plants, but they're common elsewhere too.

Juvenile (left) and adult foliage of mataī (Prumnopitys taxifolia)

 Secondly, small genetic differences can lead to quite big visible differences in plants or animals that belong to the same species.  Some of these are simple polymorphisms, like eye colour in humans.  In Veronica amplexicaulis, a hairy form used to be distinguished as a separate species (Garnock-Jones & Molloy 1983, under the old name Hebe amplexicaulis).  But it turns out this difference is the product of two alleles of a single gene, as are occasional flower colour variants in many plants.

White and blue viper's bugloss, Echium vulgare, growing side by side (Black Birch Range, Marlborough).

Thirdly, local populations might adapt to special conditions.  On mine tailings, where toxic heavy metals pollute the soil, plants may acquire tolerance, and this could involve some differences in form or in underlying physiology, yet they still freely mate with the non-tolerant individuals nearby.  These are classified as ecotypes, but not as separate species.  The differences are maintained by strong selection, even in spite of free gene flow between the tolerant and intolerant plants.

The form of Veronica albicans that grows on the dolomite outcrop at Mt Burnett looks a little different from other populations of this variable species; it might have adapted to its substrate, yet there's no evidence that it can't exchange genes with the rest of its species.

 Fourthly, some plants and animals are able to alter their form to cope with different environments they find themselves in or to escape predators—phenotypic plasticity or polyphenism.  Some inchworm caterpillars develop different appearances to blend in with the foliage of whatever host plants they’re living on (Greene 1989).  The underwater and aerial leaves of aquatic plants can be hugely different.  Plants can have very different leaf shapes, or even leaf anatomy, depending on the amount of sunlight they’re receiving or even what season they’re in.

Eryngium vesiculosum has very different leaves in summer (above) and winter (Webb 1984).

In all four of these situations, the result is two different looking plants growing together side by side, giving the appearance of two distinct species that aren’t interbreeding.  That’s just the sort of thing that gets taxonomists and field botanists excited, because we always like to discover a new species.

On the other hand, the reverse situation can arise.  Two species can look so similar that their existence isn’t even suspected until genetic tests are done.  These are called cryptic species.

It’s important to be aware of these possibilities, and in fact to rule them out as explanations before jumping to the conclusion that the variation we’re observing is due to the existence of more than one species.  The idea that two different-looking plants growing side by side must be different species is simplistic, yet "side by side" has become a bit of a mantra in some circles.

One way to test these potential new species is by growing different-looking plants together in uniform environments—common garden experiments—and also growing genetically identical plants in different environments—reciprocal clone transplants.  These approaches were pioneered in the first half of last century by Swedish botanist Turesson and by American botanists Clausen, Keck, & Hiesey.

Veronica lanceolata in flower, Rimutaka Range.

The speedwell hebe Veronica lanceolata is widespread in the North Island of New Zealand and a few parts of the South Island.  Each region has its own form of the species and, in general, adjacent populations are quite similar.  With some familiarity, it’s possible to tell from its appearance where a plant has come from.  These differences are maintained in common garden experiments, but I don’t regard these forms as different species because they can cross freely, their flowers and fruits are very similar, the differences are quantitative rather than qualitative, they have the same chromosome number, and the changes are mostly gradual and continuous from place to place.

Each leaf is from a different population of Veronica lanceolata.

However, there are places where two very different-looking forms grow together side by side, and this is exactly the sort of situation where a simplistic "side by side" approach might lead a botanist to the view that two species are involved.  In the Ruahine and Kaimanawa Ranges, especially on limestone cliffs, there are low-growing small leaved plants growing together with bushier large-leaved plants.  Although their leaves and stems are different in size and stature, their flowers and fruits are the same, which is a bit of a clue that these plants are responding in a plastic way to their environments, that there are no underlying genetic differences, and no breeding barriers between them.  I’d always assumed so at any rate, even though some field botanists made numerous collections of both forms, mounted them as separate accessions, and labelled them to highlight the differences and the fact they grew together side by side.  The hint was implicit: these might be different species.  Perhaps fortunately, nobody had the confidence in their hunch to give them different names.

South end of the Maungaharuru Range.

A couple of summers ago I was in the Maungaharuru Range in central Hawkes Bay with my colleague Heidi Meudt from Te Papa.  We were looking for forget-me-nots along the tops for a detailed genetic study she's conducting into their taxonomy and evolution.  Along the cliffs at the south end of the range we found Veronica lanceolata growing in mostly shady sites among mosses and algae.  But when we stumbled into some sink-holes things got interesting.  Here were moist shady sites with quite large-leaved plants, very close to sunny outcrops with tiny creeping plants.  It was an ideal opportunity to test my hunch that these were just plastic responses to moisture and shade.

There wasn’t room in the garden at home for a large randomised trial, so I sampled just a couple of plants of each type from sites only a few metres apart, and brought them home to grow in pots.  I also pressed branches of each, to record and preserve how they had looked in the wild.

Collection 2834, small and large leaved plants just after potting, Feb 2011.

Collection 2836, a small leaved plant just after potting, Feb 2011. The white plastic labels are 13 mm wide.

They’ve been growing now for about 18 months, and some, but not all, of the changes are quite dramatic.  For 2384, the small-leaved plant now has somewhat bigger leaves, but it's still distinctly smaller than the large-leaved plants.  For 2836, leaves are now up to 20 mm long, whereas they were about 5 mm before.

Both surfaces of the largest leaves from each of the three plants (two from 2836 small), Sep 2012.

So the results are a bit mixed, and this shows how important it is to use large samples, not just a couple of plants, and to randomise the trial properly.  The plants have exhibited some phenotypic plasticity but that doesn't account for all the differences.  Note also the two very different leaf shapes from the same plant of 2836: more evidence of plasticity.  Maybe both phenotypic plasticity and ecotypic differentiation are happening in this population.  Next time I'm in a position to collect a bigger sample and repeat this experiment I will do so.  In the meantime, I can try crossing the small- and big-leaved plants this summer.  My expectation is the offspring will be fully fertile.

With these speedwell hebes, the differences in growth form and leaf shape are striking, but they aren’t sufficient to compel rejection of the hypothesis that they’re the same species, because there are two different and simpler explanations—phenotypic plasticity and ecotypic differentiation—for that pattern.  My simple experiment hasn't clearly demonstrated which is happening, because the experimental design and sampling are insufficient.  But it's important to note also that these are quantitative differences—leaf shape and size—just the sorts of things that often vary in natural populations.

I'm sure it’s possible to test species status scientifically and explicitly.  That means starting with a testable hypothesis.  It’s better to start with the hypothesis that the two entities are conspecific, because any differences are evidence to the contrary that would compel us to reject the hypothesis.  If instead we start with the hypothesis that they’re different species, it’s hard to imagine how many similarities between them would compel us to reject that idea.  And if we start with the hypothesis that there are two species, and then seek evidence to support the hypothesis, then we're not doing science, at least not as it was formulated by Karl Popper.

References

Garnock-Jones, P.J.; Molloy, B.P.J. 1983.  Polymorphism and the taxonomic status of the
Hebe amplexicaulis complex (Scrophulariaceae).  New Zealand Journal of Botany 20: 391–399.

Greene, E. 1989. A diet-induced developmental polymorphism in a caterpillar. Science 243: 643-646.

Le Comte, J.R.; Webb, C.J. 1981.   Aciphylla townsonii — a juvenile form of A. hookeri (Umbelliferae).  New Zealand Journal of Botany 19: 187–191.

Webb, C.J. 1984.  Heterophylly in Eryngium vesiculosum (Umbelliferae). New Zealand Journal of Botany 22: 29–33.

Wednesday wildflower: bluebell

Bluebells, Hyacinthoides non-scripta,
in woods at Wokingham, England

The English bluebell, Hyacinthoides non-scripta, is a familar and much-loved spring flower.  In woods throughout Britain it comes up and flowers as part of a cycle of spring flowers on the forest floor, along with lesser celandine (Ranunculus ficaria) and greater stitchwort (Stellaria holostea).  Each of them blooms for about a week, and then the leaves appear on the trees and the understory becomes dark and shady.

In Britain and in gardens here too, Hyacinthoides non-scripta has often hybridised with the Spanish bluebell, H. hispanica, which has larger flowers and appears to be a more vigorous plant.  The hybrids have wider leaves, more flowers on a stalk, and pedicels longer than the flowers.

Drifts of bluebells in spring can take your breath away.  A few weeks ago when I wrote that groundsel was probably the first weed I learned the name of, I certainly wasn't thinking of bluebell as a weed.  My first plant memory is of bluebells in the woods near Stafford Castle.  We'd gone for a family walk (I was probably 4 because we moved away from Stafford before I was 5, but it's possible I was 3).  I remember there was a tree house, and great drifts of bluebells under the trees.  There's a scene in the movie Ryan's Daughter, which reminded me of that sight (bluebells at 22 seconds into the trailer at the link).

Bluebells and greater stitchwort, Wokingham

Bluebells, Hyacinthoides hispanica or H. xmassartiana, Wellington Botanic Garden

Bluebells are grown commonly enough in New Zealand gardens. Occasionally they can be found in the wild, perhaps establishing from bulbs discarded with garden waste by people who dump their garden rubbish at the roadside instead of at the tip (or better, composting it).  I'm always pleased to see them (bluebells, that is), and regard them as a wildflower rather than a weed.  I've seen quite a few patches this week.

Wild bluebells, Hyacinthoides xmassartiana, Norway St steps, Kelburn, Wellington.

This flowers below are from a roadside clump in Highbury, Wellington, in a roadside weedy patch that has provided subjects for other entries in this blog.  The flowers are pale and arranged on all sides of the stalk, features on H. hispanica, but they have white pollen, a feature of H. non-scripta.  Almost certainly they are derived from hybrids, and should therefore be called H. xmassartiana.

Bluebells, Hyacinthoides xmassartiana, Highbury, Wellington.

In Scotland, Scandinavia, and Australasia the name bluebell is also given to harebells, or members of the Campanulaceae, such as Campanula rotundifolia (blåklocka in Sweden) and Wahlenbergia.

Wednesday wildflower: groundsel.

When I was young, about 11 or 12 I guess, I caught a budgie on the neighbor's front lawn.  I spotted him through the kitchen window, a flash of brilliant blue struggling against the Wellington wind.  When he settled on the lawn I ran over there and flung my tee shirt over him, and carefully carried him home.  We tried to find his owner, but eventually we gave up and Bluey became part of our household.  I never managed to teach him to talk, but he did have a cheerful whistle.

The neighbors told me to hang a sprig of groundsel in his cage, so I'm pretty sure groundsel was one of the first weeds I ever learned the name for.  I scoured the garden for it, and even today I always notice groundsel, even though it must be 45 years since Bluey died.

Senecio vulgaris leaves (A, abaxial; B, adaxial) and flower heads at flowering (C), early fruiting (D) and after fruiting (E).

Groundsel, Senecio vulgaris, is a common weed of cultivated ground.  The flower heads lack ray florets, but are otherwise similar to other senecioids, like Roldana.  The loss of rays and the smaller stigmas in S. vulgaris suggest self-pollination, but the mating system seems not at all straight-forward.  Some plants in Europe do produce rays, but New Zealand populations of S. vulgaris are reported to be all rayless (Webb et al., 1988).  Ray production is controlled by a group of regulatory genes, which are expressed (or not) in the outer florets of a head (Kim et al., 2008).  In conditions where self-pollination is advantageous, raylessness is favoured.

References.

Kim, M; Cui, M.-L.; Cubas, P.; Gillies, A.; Lee, K.; Chapman, M.A.; Abbott, R.J.; Coen, E. 2008: Regulatory genes control a key morphological and ecological trait transferred between species.  Science 322: 1116–1119.

Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. 1988.  Flora of New Zealand Vol. 4.  DSIR, Christchurch.

Identification

Many people think of botanists simply as people who can rattle off the Latin names of plants.  Charles Dickens seemed to be reflecting this with his character Wackford Squeers in Nicholas Nickelby: 

• "... bottiney, noun substantive, a knowledge of plants.  When he has learned that bottiney means a knowledge of plants, he goes and knows 'em.  That's our system Nickelby, what do you think of it?"

Biological identification is the process of assigning a biological sample to membership of a group.  Usually it means giving it a name.  If we're talking about a species level identification, we're making a judgement that the sample belongs to a particular species rather than any other.  Say you see a small four-legged furry animal and you say it's a cat.  What is the process behind that decision?

Rufus, a cat.

First, what is a cat?  In common English language uses, cat could mean one of a number of things.  It could be the biological species Felis catus, the domestic cat.  It could be any one of the other species in the cat family, such as a lion or a tiger.  Or it could be one of a number of other animals that are not strictly cats, such as the meerkat or the civet cat.  In other languages there are other names, le chat in French, el gato in Spanish.  In biology though, the scientific name for the domestic cat, Felis catus, is international and more importantly it's strictly defined by a type specimen, usually a museum specimen that is permanently attached to the scientific name, for reference and stability.  If you try to tell me a meerkat is Felis catus, we can compare it with the type specimen and see if you're right.

But even then, it's not entirely objective, because we're using the process of identification.  Technically we're looking for identity between the type specimen of Felis catus and our meerkat.  And strictly speaking, individuals in the same species are rarely identical (even identical twins have different fingerprints).  So whether two individuals are the same species or not is often a matter of opinion.  Thus we use the term identity in the sense of belonging.

Because of the type system in biology, we can say the type specimen is Felis catus, but every other cat is only identified as Felis catus.  It's a matter of opinion that they belong to the same species, but in the case of cats, and even more of our own species, that opinion is based on a considerable amount of experience and knowledge.  When it comes to organisms that are less like us, it becomes harder to decide if two individuals belong to the same species or not.  Unicellular algae can appear to be identical, yet be unable to interbreed and have quite different DNA sequences.

Branches from this plant near Franz Josef Glacier were collected, pressed, and mounted as a herbarium specimen to be the type specimen of Veronica colostylis (although originally it was called Parahebe linifolia subsp. brevistylis).  Advance of the glacier has wiped out that locality, but plants of the species are still common in the valley, and the type specimen is preserved in the Allan Herbarium at Landcare Research, with duplicates in several other herbaria.

There are many different ways that biologists decide which individuals belong to the same species, sometimes called species concepts.  The best functional definition is the Biological Species Concept (BSC), because this is a genetic definition: a species is a breeding population, or group of interbreeding populations.  Genetically, a species has a gene pool, made up of all the different alleles (gene variants) that are capable of being combined with each other because they're found in individuals that can interbreed.  An allele that's only found in a dog will never combine in nature with one that's only found in a cat, because these two are different species and can't be interbred.

DNA sequencing gel

While the BSC is a useful conceptual and functional definition of a species, it's not used very often to identify individual specimens.  It's simply too bothersome and time-consuming to try all the interbreeding experiments that might be necessary.  Instead, we use a proxy.  Often it's their morphology (the Morphological Species Concept or MSC): if two individuals look the same, or at least very similar, they're reckoned to belong to the same species.  And if we want to give our sample a name, we need to compare it either directly or indirectly (through a description or photograph) with a type specimen.  Recently there's been a lot of interest in using short DNA sequences as identification markers for species, so-called DNA barcodes.

 Morphology works as a proxy for the BSC because we know empirically that members of the same biological species usually look very similar.  But two problems arise with the Morphological Species Concept.  First, species can be very varied.  Sometimes males and females look very different, some barnacles for example.  Other times, juveniles and adults can look so different they're mistakenly classified as different species, as in many kinds of eels.  Sometimes there are polymorphisms like striking colour variants within a breeding population.  In plants and some animals, different forms may be produced in different environments, like the inchworms that grow to be camouflaged on whatever host plant or plant part they're feeding on, or at different times of the year.

Secondly, there are cryptic species, those that look the same but are separate breeding populations.  Sometimes they have physical, timing, or genetic barriers to successful mating, but if we rely on the MSC we'll not discover these.

Veronica odora plants in the North Island and northern South Island (also in the Auckland Islands) have two sets of chromosomes (diploid), but in the central and southern South Island they have four sets (tetraploid).  Probably these two chromosome races can't interbreed and should perhaps be treated as cryptic species, even though I've found no way they can be distinguished based on their morphology.

 So a biological identification is a matter of opinion, but that certainly doesn't mean anyone's opinion is as good as anyone else's.  Taxonomists who study the classification of groups and who understand the nature of their variation and breeding relationships will be more reliable than Wackford Squeers who just "knows 'em".  That's because their identifications are based on a sound understanding of the evidence.  And we can future-proof and error-proof our identifications by keeping a record of what the plant or animal was, preferably as a museum specimen.  That way, if we got it wrong or if the name changes in the future, someone can always check back and bring the identification up to date.  A name in a notebook, publication, or database that hasn't been safeguarded in this way is practically valueless.

Specimens are also important for resolving disagreements about identification.  I remember being called once by a botanist who firmly told me not only had I got the distribution of Sonchus arvensis wrong in a Flora treatment (Webb et al. 1988), but I hadn't described it accurately either.  Fortunately my initial horror and embarrassment gave way pretty quickly to a potential alternative hypothesis, so I asked for a specimen to be sent by mail.  You can guess where this is going, I hope: to my relief, the specimen was Picris echioides.