biogeography Archives

19/01/202219/01/2022

Tramps in Transition: Wallacea’s monarch flycatchers and their evolutionary natural experiment

Pale-blue Monarch on the left and Island Monarch on the right

A warm welcome back to all our readers! The new year is now well and truly upon us and we hope you’ve all had a safe and energised return to work. This blog is written by Fionn Ó Marcaigh, summarising his new paper. Congratulations Fionn and we hope our readers enjoy learning about your research as much as we have! So without further ado…

Science is about making observations from the natural world, drawing up hypotheses to explain the patterns you’ve observed, and then testing these hypotheses by experimentation. We tend to imagine scientists in white coats doing experiments in the lab, but our understanding of evolution also owes a lot to work done in “natural laboratories” like islands and other isolated habitats, where evolution has taken place under different conditions. Our new paper, just published Open Access by the International Biogeography Society in their journal Frontiers of Biogeography, has used an important natural laboratory in Southeast Asia to test a classic hypothesis based on a bird called the Island Monarch (Monarcha cinerascens). We’ve made observations that contradict parts of the hypothesis and discovered a possible new species in the process!

Our natural laboratory was a collection of islands around a region known as Wallacea in central Indonesia (see map below). Named after Alfred Russel Wallace, this is where he co-discovered evolution by natural selection while travelling around islands of all shapes and sizes, with the waters around them being so wide and deep that most species have trouble crossing them. Some organisms are better at crossing these barriers than others, with the Island Monarch thought to be particularly adept. As its name suggests, the Island Monarch is one of the kings of small islands. It can be found all the way from the islands off Sulawesi in Wallacea, to the farthest reaches of the Melanesian islands east of Papua New Guinea, but is missing from large islands like Sulawesi and New Guinea themselves.

14/07/202114/07/2021

Evolution in the understorey

What is the first image that comes to mind when you think of evolution? Possibly a line of cartoon primates marching, slouching monkeys at one end and naked men with spears at the other. Or a branching tree diagram where each twig represents an organism, maybe with a tentative “I think” scribbled above it. Alternatively, you may have pictured an illustration of related birds from isolated islands, each showing a dramatically different bill shape adapted to a different diet. Darwin’s Galápagos finches represent a foundational influence in terms of where we tend to look for signs of evolution and what we expect these signs to look like. Our new paper, just published Open Access in Zoologischer Anzeiger: A Journal of Comparative Zoology, provides a contrasting image. We looked at the Sulawesi babbler (Pellorneum celebense), a dull brown bird that spends its time hiding in bushes on less isolated islands in Indonesia, looking pretty similar from one island to the next. Nevertheless, we found that several of its populations are quite different from one another in mitochondrial DNA, in morphology, and in song.

07/10/202009/10/2020

Shy birds hiding evolutionary insights: cryptic sexual dimorphism in the Sulawesi Babbler

The most iconic examples of sexual dimorphism are found in birds. Birds are probably many people’s introduction to this concept in the natural world, when brought to the park as a child and shown the difference between male and female mallards. But sexual dimorphism can be much more subtle than that kind of difference in colour (called dichromatism, and seen also in peacocks, pheasants, sparrows, and many more). Our new paper, just published by the Association for Tropical Biology and Conservation in their journal Biotropica, shows that sexual dimorphism can be missed in some birds even when it is important to their ecology and evolution.

24/09/201924/09/2019

Birds in paradise: biogeography in the subtropics

Light-vented bulbul (Pycnonotus sinensis), one of the species of interest in the Ryūkyū archipelago

The species-area relationship is considered one of the only ‘rules’ in ecology. We have observed more species on larger ‘islands’ (whether true islands or simply some habitat patch of interest) in studies of different plants and animals all around the world. When MacArthur and Wilson (1967) proposed this pattern and the pioneering biogeographical principles which underpin it, they acknowledged that a piece of the puzzle was missing: species identity.