Melicope: Hawaii's export to the Pacific

Over the years, the general consensus has been that islands of the Pacific, and particularly the incredibly isolated archipelago we fondly know as Hawaii have been the passive collectors of fauna and flora that have just happened to have swum, flown, drifted, or been blown onto their fair shores. It's generally been thought to have been a one-way process, that once something has arrived there, it settles down and makes the most of their tropical paradise. Something that those of us stuck in cold climates can relate to very well -- why would you want to leave a place that is extremely amiable and is yours for the taking?

However, recent systematic research on a number of organisms is starting to shake up this tidy story somewhat. It appears that we may have underestimated the ability of these islands to send their biota elsewhere.

The particular paper sparking this post, written by Danica Harbaugh and coauthors, features the shrub Melicope. It's widely distributed across Asia and the South Pacific, but has undergone an "explosive radiation" in Hawaii, with 47 species found in the group. As usual, the authors hypothesised that all Hawaiian species had originated from a single colonisation and formed a monophyletic group restricted to the islands. Data from a number of genes were analysed, and it was found that although it does seem to be the case that all Hawaiian Melicope were derived from a single colonisation, it hasn't remained stuck in the one place. Surprisingly, their data suggested that Hawaii has exported some of their plants to the Marquesas Islands, where they have subsequently speciated.

This data adds to the body of work that suggests that Pacific biogeography is a lot more dynamic and complicated than initially suspected. It is also another example of the very intriguing connection that exists between Hawaii and the Marquesas.

References:
Harbaugh DT, Wagner EI, Allan GJ, Zimmer EA. 2009. The Hawaiian Archipleago is a stepping stone for dispersal in the Pacific: an example from the plant genus Melicope (Rutaceae). Journal of Biogeography 36: 230-241.

Tokelau Ant Communities

Tokelau is a small place, far away from anywhere. Unfortunately, like all Pacific Islands, it has been overrun by invasive ants, which have massive impacts on the ecosystem of the islands. Phil Lester and his crew from Victoria University in Wellington, New Zealand made the most of a bad thing and took the opportunity to investigate community structure and assembly processes on these islands. What they did which few others have done was investigate the effect of abundance on community assembly, as opposed to just recording which species are found in the same places as each other. As expected, they found that as the abundance of ants went up, the number of species present decreased.

The ant that was dominant, was the yellow crazy ant, Anoplolepis gracilipes. And boy, was it dominant! Maximum abundances were 100 times that of the most abundant species. Rather unsurprisingly, the authors comment that

"in high abundance, A. gracilipes was associated with reductions in the number of co-occurring species and their abundance."

In this research, the authors only looked at the effect on other ant, which are also introduced to Tokelau. However, the effect of the ants can be devestating. One of the most publicised crazy ant invasions is their effect on the ecosystem of Christmas Island, Indian Ocean, home to the charismatic red land crab. A couple of reports about the invasion in the popular press are this one from the ABC and a report from the Australian Government

Reference:
PJ Lester, KL Abbott M Sarty and KC Burns. 2009. Competitive assembly of South Pacific invasive ant communities. BMC Ecology 9:3

Pacific Regional Red List

The Red List, a rather grim survey of the state of the world's biodiversity that highlights which species are particularly under threat of extinction, is one of the signature products of the IUCN. It is global in scope which gives it wide applicability, but sometimes details get lost in the mass of data. For example a search of "Pacific" in the list results in 160 entries, a number of which are not taxa from the the Pacific Islands, and those that are are primarily made up of the French Polynesian species Partula land snails.

This month however, IUCN have reviewed a number of species in preparation for a regional red list for the South Pacific, and have published a draft available at this website. It's a decent piece of work: 3769 species have been assessed, of which (to look at the bright side of things!) 1605 are considered to be of least concern. The worrying thing is that nearly the equivalent number (1060) are considered to be in threat of extinction, 177 of which are critically so.

There has been some discussion about the usefulness and validity of these documents, particularly for non-vertebrates. I see with some mirth that they confidently state the estimated number of described species to be 4911 (love the precision!), and I like the comment "Even experts contributing to global species assessments are often unable to provide an accurate estimate of the number of known species". Even experts eh...

Fruit bats going the wrong way

A couple of years back, Jeremy Pulvers and Don Colgan published an interesting paper on the intriguing fruit bat genus Melonycteris, that is restricted to the Solomon Islands and the Bismarck Archipelago. The fascinating thing about this bat is that it is believed to be placed right at the base of the Megachiroptera (flying foxes and their ilk). Why it is that this supposedly old lineage is restricted to these isolated island groups is still unknown, but it is not alone in this pattern. In the birds, a number of the more ancient groups are found in and around New Guinea and the Australasian region.

This however, is not the thrust of the Pulvers and Colgan paper. What they did is look at the genetic systematics and variation within the genus, particularly the Solomon Island species. To summarise, they found that the Solomon species are a group separate from the single Bismarck species. What was more interesting was the pattern of relationships within the Solomon Islands population. They found that the species on Makira (San Cristobal) was sister to the rest, followed by the Malaitan species, then the species found in the New Georgia group. Choiseul, Isabel and Guadalcanal populations composed a single group and were the most derived.

What is interesting about this pattern is that it is the opposite of what would be expected from a simple dispersal model originating in the Bismarcks. If that was the case, you would expect the sequence to be essentially the opposite---New Georgia; Choiseul, Isabel and Guadalcanal; Malaita, then Makira.

There has been increasing evidence from birds that the "Dispersal from New Guinea" model of the makeup of the Solomon Island fauna is not the only story, but as far as I'm aware, this is the first publication of evidence in vertebrates other than birds.

Reference:
Pulvers JN, Colgan DJ. 2007. Molecular phylogeography of the fruit bat genus Melonycteris in northern Melanesia. Journal of Biogeography 34:713-723.

The Prescient Baron

"We put in at Namuka Bay ... and there visited the Navesi saw-pits. The owner ... has acquired considerable knowledge of the native timber. He says that if people were not so prejudiced he could prove to them that Fiji produces wood equal to any imported. As yet much of the forest is untouched, but the supply in an island the size of Viti Levu, especially when considerable tracts of its surface are bare, can by by no means inexhaustible. An instance in point; the sandalwood forests of Vanua Levu, which first brought the Fijian Islands into note by attracting traders to their shores, have for some time ceased to exist, and the trees have been felled so assiduously as almost to exterminate the Santalum yasi in this island. This is a fact that ought not to be lost sight of, and the sooner stringent laws are brought into force for the regulation of tree felling, the better for the future prospects of the colony."

The Baron Anatole von Hügel wrote these words on his trip from Levuka to Sigatoka in 1875. He spent two years in Fiji collecting birds and buying traditional objects for the Cambridge Museum. His journals are a fascinating and informative read of Fiji in the early days of colonisation.

His remarks above are remarkably foresighted, but have sadly gone unheeded. No doubt if he were around to visit Fiji today both him and his sawmilling friend would be dismayed to find extensive plantations of mahogany and pine, and very little legislation protecting and regulating logging.

Those who cannot learn from history are doomed to repeat it.

References:
Roth J and Hooper S (Eds). 1990. The Fiji Journals of Baron Anatole von Hügel. Fiji Museum, Suva.

The bizarre family of the Silktail

The silktail (Lamprolia victoriae) is a small bush bird, restricted to the Fijian islands of Vanua Levu and Taveuni. From its first description in 1874 its systematic position has been debated with suggested closest relatives ranging from the australian robins (Petroicidae), and the monarch flycatchers (Monarchidae), to the birds of paradise (Paradisaeidae). The late, great Ernst Mayr famously called the silktail "One of the most puzzling birds of the world". Last year, a group of european, american and south african scientists headed up by Martin Irestedt brought DNA evidence to the party to shed further light on the subject. Their results were published here.

What they discovered was totally unexpected. Their data suggests that the closest living relative to the silktail is the Papuan mountain drongo (PMD, Chaetorhynchus papuensis), a little-known bird of the New Guinea highlands. The PMD has traditionally been grouped with the drongos (Dicruridae), but in the Irestedt study, both the silktail and PMD are sister to the fantail family (Rhipiduridae).

The authors discuss at length the biogeographic implications of their finding, suggesting either long distance dispersal or a vicariant metapopulation origin, but are unable to come to a conclusion either way. Unfortunately, they don't suggest ways of testing these hypotheses. I suggets it may be a little premature to speculate too seriously about this single result, interesting though it is. Future work on the geology of the region and further systematic research on the silktail and the remainder of the avifauna of Melanesia may reveal other potential explanations.

References:
Irestedt M., Ruchs J., Jonsson K., Ohlson J. I., Pasquet E., Ericson P. G. P. (2008) The systematic affinity of the enigmatic Lamprolia victoriae (Aves: Passeriformes) - An example of avian dispersal between New Guinea and Fiji over Miocene intermittent land bridges? Molecular Phylogenetics and Evolution 48: 1218-1222

Picture courtesy of Birdlife International

Curiosities of Biological Nomenclature

This is a site that I always try to find when I'm wanting a bit of light humour. It is a list of humorous scientific names of all sorts of taxa. In here you discover that Nirvana is a leafhopper, Dracula is an orchid, and the moth Dyaria was named in 'honor' of one Mr Dyar...

It's funny.

http://www.curioustaxonomy.net/index.html