The Great Veronica Hunt —Part 6.

I'm writing this in Melbourne, where I'm about to fly home after a wonderful three weeks in Australia. I wasn't specifically on a Veronica hunt, but kept my eyes open anyway, just in case.

I didn't see any Veronica in Queensland or around Sydney. The first I saw was the introduced V. arvensis in Bega, a small New South Wales town.  Australia has many of the same weedy speedwells that New Zealand does, so I was more interested to see plants of the indigenous species.

Mallacoota inlet, Vic.

We spent a couple of days with friends at Mallacoota in the far east of Victoria, and there came across V. plebeia growing beside a track in coastal forest in the wonderfully-named Croajingalong National Park.

Veronica plebeia, Mallacoota, Vic.

The flowers were closed just as they often are in New Zealand, needing a warm sunny day to open.  If they don't get to open, I assume they self-pollinate, because they always seem to set fruits.

The flower below was photographed on a cultivated plant in New Zealand, where V. plebeia is widespread and considered by some botanists to be native.  It is introduced and weedy in some other parts of the world though, so it does have the ability to be invasive.

Veronica plebeia, from a cultivated plant in New Zealand.

That was it for wild speedwells the whole trip, but my sister-in-law, near Ballarat, had some small plants of another Australian native, Veronica gracilis, ready to plant out in the garden, and one of these was in flower.

Veronica gracilis, cultivated near Ballarat, Vic.

The plants are strongly rhizomatous, and this one even had a shoot coming out of the drainage hole in the bottom of its pot.

Australia has 23 native species of Veronica, classified in section Labiatoides, and they are the sister group to the large New Zealand clade (section Hebe) that includes the hebes and their relatives (Albach & Briggs 2012).  Thus, although they look much more like northern speedwells than New Zealand hebes, they are known to be more closely related to the hebes.  And because of that fact, it's misleading to classify them as Veronica unless you classify our hebes in Veronica as well.

Reference

Albach, D; Briggs, BG. 2012. Phylogenetic analysis of Australian species of Veronica (V. section Labiatoides; Plantaginaceae). Australian Systematic Botany, 2012, 25, 353–363
http://dx.doi.org/10.1071/SB12014

Wednesday wildflower: Diddillibah wildflowers.

This week I’m on the Sunshine Coast, Queensland, visiting family before the Australasian Systematic Botany Society’s conference in Sydney next week.  We arrived last night and this morning took a short walk to get a feel for our surroundings, from Diddillibah to the Maroochy River and back.

Maroochy River

We haven’t seen much natural vegetation yet, but plenty of wildflowers and a few native Eucalypts and she-oaks.

Mangroves, Maroochy River.

Along the river are mangroves, which I assume are the same as we have in New Zealand, Avicennia marina.  It reaches its southern limit—and the southern limit of mangroves generally—at Corner Inlet, Victoria.  Here, in the warmer climate, they grow taller.

Mistletoe in a Casuarina tree.

There were mistletoes in the she-oak (Casuarina) trees near the river.

Mistletoe flower buds.

I think this little weed is Emilia sonchifolia, something I’ve collected before, in Singapore; at least I think it’s the same.  

Emilia sonchifolia

Its resemblance to sow-thistle (Sonchus) is remarkable, but it’s convergence, because this isn’t in the same tribe.

Emilia sonchifolia flower head.

The single row of involucral bracts is characteristic of tribe Senecioneae, whereas Sonchus is in the Lactuceae.

And there was a pelican on the river. Nice.

A new classification for the southern beeches.

In New Zealand, the forest we typically identify with—the “bush”— is the lowland mixed conifer-angiosperm forest, with a canopy usually of angiosperm trees like tawa (Beilschmiedia tawa) or kamahi (Weinmannia racemosa) and large emergent conifers of the southern families Podocarpaceae (e.g., rimu, Dacrydium cupressinum) and Araucariaceae (i.e., kauri, Agathis australis).  But in most montane parts of the South Island (Te Wai Pounamu) and on often drier ridges and hill country of the North Island (Te Ika A Māui), a very different type of forest is dominant.  This forest comprises a uniform canopy of often a single species of southern beech.  Usually the forest doesn’t have a dense understory, giving an open and well-lit appearance to the interior.  This is just as much an iconic New Zealand forest as the “bush”, and one that’s familiar to many trampers.

Southern beech forest, Orongorongo Valley, near Wellington

Similar forests are found in the southern part of South America, so that travelers there from New Zealand often feel it’s just like home.  Southern beech forest also occurs in Australia, New Guinea and New Caledonia.  It’s known from fossils in Antarctica too, going back to the Cretaceous, as well as in many of the places where it still occurs today.

The southern beeches were originally classified in the genus Fagus, along with their northern namesakes, but by 1850 their differences had been recognised and they were transferred to the genus Nothofagus (the name means southern beech [correction, 21 Nov 2013: it means "false beech"; southern beech would be Notofagus.  H/T Rosi]).  As Nothofagus, the southern beeches have been important trees in New Zealand ecology, conservation, forestry, and biogeography.  Whole books have been written about them.  Nothofagus is currently reckoned to have about 40 species.  In 1962, a Russian botanist, Lyudmila Kuprianova, went a step further and proposed a new family, Nothofagaceae, for the southern beeches.  This took rather a while to be accepted.

Many botanists have wrestled with the relationships of the species within Nothofagus, using sometimes single or few characteristics, other times multiple ones.  The advents of (1) cladistic thinking (using explicit evolutionary trees) and (2) molecular characteristics from DNA sequencing have been of major help to this enterprise, because DNA has provided a wealth of new characters that are independent of the morphological ones and because the analysis and interpretation are out in the open for everyone to evaluate.  Pretty quickly, the understanding of relationships in the southern beeches has converged on a single well-supported arrangement, which was arranged into a classification by Australian botanists Bob Hill and Jenny Read, who recognised one genus (Nothofagus) with four subgenera.

Southern beech forest near Eastbourne, Wellington.

Beyond the southern beeches, DNA sequence data were also telling us a lot about the relationships of southern beeches to the oaks, beeches, chestnuts and she-oaks and it became pretty clear that Kuprianova was correct in isolating them in their own family.  It turns out that the ancestor of the beech order (Order Fagales) first divided into two species: one that was the common ancestor of the northern sweet chestnuts, beeches & oaks, she-oaks, myrtles, and more—seven families in all—and the other that was the common ancestor of just Nothofagus.  If you were to divide Fagales into two suborders, one would have seven families and many genera, the other would have just one family, and that family would have just one genus.  Thus Nothofagus and Nothofagaceae have different ranks (their place in the hierarchical classification) but identical circumscriptions (the species they contain); that redundancy means we're not using the available hierarchy of ranks to full advantage.

What’s more, the current classification of all the southern beeches in one genus Nothofagus can be a bit misleading.  Most biologists agree that it’s absolutely essential that every genus or family should contain closest relatives.  In other words, a species shouldn’t be more closely related to a member of another genus than it is to a species that’s classified in its own genus.  Nothofagus doesn’t break that rule: every species of Nothofagus is more closely related to every other species than it is to any species that’s not placed in Nothofagus.  So far, so good.

But it’s easy to assume that our New Zealand species—black, hard, red, mountain and silver beeches—might be each other’s nearest relatives, and often people are surprised to find that’s not the case.  In fact, hard, black, mountain, and red beeches are related, but silver beech’s nearest relative is in Australia.  Wouldn’t it be better if their classification and their scientific names could reflect that?

This week two New Zealand botanists, Peter Heenan and Rob Smissen from Landcare Research, have revisited the classification of the southern beeches (Heenan & Smissen 2013).  They brought together everything that’s been published so far, from both morphology and molecular systematics, and added some new data and analyses of their own.  Their findings are pretty much the same as several previous reports, but they can now place greater levels of confidence in the groups they recognise.  They comprehensively discuss alternative classifications and alternative criteria and come down with what I think is the most sensible classification. 

Nothfagaceae now contains four genera.

• Nothofagus comprises just five species from temperate South America.  The rest of the family is no longer classified as Nothofagus.
• Lophozonia is a reinstated genus, containing seven species from South America, New Zealand, and Australia.  
• Fuscospora has six species and a very similar distribution; it’s a newly recognised genus, although like the others it has been treated as a subgenus in the past.  Additionally in Fuscospora, this paper promotes mountain beech to species rank as F. cliffortioides.  I look forward to reading the evidence for that change, because it was previously treated just as a variety of black beech.
• Finally, Trisyngyne is the largest genus (25 species) and found today in the tropics: New Caledonia, Papua New Guinea and extending into Indonesia.  

These genera are strongly supported by both molecular, morphological, and chemical characteristics, and they have symbiotic fungi and parasitic fungi and insects that also seem to recognise their relationships.

Red beech, Fuscospora fusca.

Black beech, Fuscospora solandri.

Mountain beech, Fuscospora cliffortioides, near Cass, Canterbury.

Hard beech, Fuscospora truncata

Silver beech, Lophozonia menziesii.

When we use these new names for the New Zealand plants, we see immediately that we have two natural groups represented here: Fuscospora and Lophozonia.  New Zealand no longer has any species of Nothofagus.

Red beech, Fuscospora fusca, Tunnel Gully near Wellington.

A final word of a more general nature.  Some people will want to reject this change, perhaps because they feel nostalgic about the name Nothofagus, or perhaps because they feel name changes are disruptive.  But taxonomy is science and there are scientific criteria involved.  Like climate change, evolution, and vaccination, you can’t simply reject sound science because you don’t like it.  

Silver beech, Lophozonia menziesii, Haast Pass.

It’s very rare in science for there to be two equally well-supported positions such that users are free to choose whichever one they prefer.  Rather, scientists make decisions after critically considering the evidence.  It's true a classification is a human construct, but it's based on facts about evolutionary history.  Those facts are hard-won data from the field, herbarium, and genetics lab.  If your opinion contradicts those facts, then you're at risk of denying the science.

In this case however, both the old classification and the new one do pass the most important test, that of classifying related species together, so we can't rule out one or the other on that ground.  The question here is, "what's the appropriate rank for these four well-supported groups?"  But is one answer better than the other?  Heenan and Smissen argue strongly and in detail that there are good reasons to prefer their new scheme over the old one.  For instance, they show that the newly-recognised genera are at least as old, diverse, and distinct as established genera in the other families of the order, that the new names are more informative about relationships among the southern beeches, and that a redundant grouping has now been eliminated.  They conclude, and I agree, that these benefits far outweigh the temporary disruption of having new names to learn.

An Australian beech, Lophozonia moorei, growing at Eastwoodhill.

Heenan, P.B.; Smissen, R.D. (2013). Revised circumscription of Nothofagus and recognition of the segregate genera Fuscospora, Lophozonia, and Trisyngyne (Nothofagaceae) Phytotaxa, 146 DOI: 10.11646/phytotaxa.146.1.1

New associations good and bad.

The word weed can be a hard one to define.  Most people accept that a weed is a plant growing where it’s unwanted, something that’s in the way, or that stops the flower or crop you’re trying to grow from growing, or interferes with valued native vegetation.  When you think about it that way, it’s clear that one person’s crop or wildflower can easily be, or become, another’s weed.  Unfortunately, the corollary is that one person’s pest might be another’s treasure.

Ngaio, Myoporum laetum.

Last week I wrote about the common confusion between New Zealand and Tasmanian ngaio, and how in New Zealand the latter is sometimes planted unintentionally in place of the former.  Our native ngaio, although prone to self-seeding in gardens and capable of fast growth, is never really a weed here.  But it is a pest plant in California, along with some others of our native flora, like pōhutukawa and cabbage trees.  This is the story of the rise and fall of ngaio in California, as told in a recent research paper by Jon Sullivan of Lincoln University (Sullivan 2013).

Ngaio was introduced into California as an ornamental tree and widely planted around the middle of last century, mostly using a California-derived cultivar, M. laetum ‘Carsonii’. It’s the 18th most common street tree in San Francisco and is valued for its fast growth and salt tolerance near the sea.  From widespread plantings in Southern California, ngaio has spread into many wild and semi-wild communities from Sonoma County southwards to Baja California in Mexico.  It forms a dense canopy that shades out other plants and the dry woody centres of the trees are considered a fire risk.  The trees even re-sprout after fire or herbicide spray treatment, so they’re hard to get rid of.

The core of Sullivan’s paper describes the effects of the chance introduction of a tiny insect, a kind of thrips (the singular and plural are both thrips).  This thrips, Klambothrips myopori,  feeds on the leaves and shoots of plants of Myoporum and seems to have got there from Australia, where New Zealand ngaio isn't native, but where other species of Myoporum are.  Although it was first described and named from Californian collections, later a small population was discovered on boobialla in Tasmania.  And its closest relative is also in Australia, so it’s likely the insect is a dinkum Aussie and a newcomer to California.  Most likely, Myoporum thrips got accidentally introduced to California, maybe via the airline routes that converge on Los Angeles.  It probably wouldn’t have become established there, except that there were already large populations of planted and weedy ngaio for it to feed upon.  

And it got stuck in.  It's taken it about five years to kill about half the ngaios in Southern California, and the remaining live ones are looking pretty sick.

Thrips are small slender insects with fringed wings.  They mostly feed on plant sap, which they do through mouth-parts that are modified for piercing plant tissue.  A thrips infestation typically produces silvery or bronze patches on shoots and leaves, where sap has been drawn out of the cells.  Affected young ngaio shoots turn brown and the leaves are distorted.  Sullivan found high densities of nymphs and adults on affected trees in California. Other thrips are pollen feeders and are often seen in flowers, where some botanists believe they can be significant pollinators.

This inadvertent spread of thrips to California is an excellent outcome for environmental managers trying to deal with the Californian ngaio outbreak.  To introduce a biological control agent these days involves a paper war of bureaucracy, and rightly so, because they can have unintended consequences.  But in California, nature—or at least accident—had already done the job.  So, all good, you might say.

The success of Myoporum thrips in California seems to support an idea that ecologists call the New Associations Hypothesis.  The idea is that when a host-specialised organism—like a thrips that feeds only on Myoporum—comes into contact with a naive host, one that hasn’t been exposed to it before, then all hell breaks loose (for the host).  The best-known historical examples are probably the human populations that hadn’t ever been exposed to European diseases, like smallpox and measles.  Because long-distance dispersal to islands is a filter that only some organisms get through, it might be that our ngaio and other native plants have evolved in New Zealand without some or all of the parasites and predators that would damage them in their countries of origin.  If they’ve let their guard down, so to speak, then introduction of those parasites and predators by human activity could be a disaster for them.

So, what if this thrips ever makes its way to New Zealand?  We now know it can and will happily eat ngaio, and we know it has the potential to hitch rides in aircraft.  It’s yet another pest we need to watch for at the border.  Presumably in Australia, the thrips and the Myoporum have evolved together and the plants have enough defenses not to be wiped out.  But we can see what might happen here by looking at Hawai'i.  There, the Myoporum thrips has already been introduced, again probably unintentionally and perhaps from California, and it’s taken to their native species of Myoporum, M. sandwicense, with gusto.

A branch of boobialla, M. insulare.

If that calamity happens here, we can only hope the thrips prefer the introduced boobialla or Tasmanian ngaio (M. insulare) to our native ngaio, M. laetum.  My guess, and Sullivan’s too, is it’s more likely to be the other way round, because boobialla is likely to have more tolerance to thrips.  Add that to people planting the wrong species, and in the future we might find our ngaio replaced by boobialla almost everywhere.

Sullivan, Jon J. (2013-08-24) Inadvertent biological control: an Australian thrips killing an invasive New Zealand tree in California. . DOI: 10.1007/s10530-013-0532-x