Integrating ecology into macroevolutionary research

On 9 March, over 150 biologists gathered in London for the Centre for Ecology and Evolution spring symposium, 'Integrating Ecology into Macroevolutionary Research'. The event brought together researchers from London-based institutions alongside others from across the UK, Europe and North America for a day of talks. The meeting highlighted methodological advances and recent analyses of exemplar datasets focusing on the exploration of the role of ecological processes in shaping macroevolutionary patterns.     

ADAPTIVE RADIATION AND THE TOPOLOGY OF LARGE PHYLOGENIES

The idea that some organisms possess adaptive features that make them more likely to speciate and/or less likely to go extinct than closely related groups, suggests that large phylogenetic trees should be unbalanced (more species should occur in the group possessing the adaptive features than in the sister group lacking such features). Several methods have been used to document this type of adaptive radiation. One problem with these attempts is that evolutionary biologists may overlook balanced phylogenies while focusing on a few impressively unbalanced ones. To overcome this potential bias, we sampled published large phylogenies without regard to tree shape. These were used to test whether or not such trees are consistently unbalanced. We used recently developed null models to demonstrate that the shapes of large phylogenetic trees: 1) are similar among angiosperms, insects, and tetrapods; 2) differ from those expected due to random selection of a phylogeny from the pool of all trees of similar size; and 3) are significantly more unbalanced than expected if species diverge at random, therefore, conforming to one prediction of adaptive radiation. This represents an important first step in documenting whether adaptive radiation has been a general feature of evolution.     

Shared and unique morphological responses of stream fishes to anthropogenic habitat alteration

Understanding population-level responses to novel selective pressures can elucidate evolutionary consequences of human-altered habitats. Stream impoundments (reservoirs) alter riverine ecosystems worldwide, exposing stream fishes to uncommon selective pressures. Assessing phenotypic trait divergence in reservoir habitats will be a first step in identifying the potential evolutionary and ecological consequences of stream impoundments. We tested for body shape divergence in four stream-adapted fishes found in both habitats within three separate basins. Shape variation among fishes was partitioned into shared (exhibited by all species) and unique (species-specific) responses to reservoir habitats. All fishes demonstrated consistent significant shared and unique morphological responses to reservoir habitats. Shared responses were linked to fin positioning, decreased body depths and larger caudal areas; traits likely related to locomotion. Unique responses were linked to head shape, suggesting species-specific responses to abiotic conditions or changes to their trophic ecology in reservoirs. Our results highlight how human-altered habitats can simultaneously drive similar and unique trait divergence in native populations.     

Ecological and morphological diversification within single species and character displacement in Mandarina,endemic land snails of the Bonin Islands

The endemic land snail species Mandarina hahajimana has undergone extensive habitat and morphological diversification within the Hahajima islands in the Bonin archipelago. This species has diversified into populations with ground, arboreal and semi-arboreal life histories. In addition, arboreal populations and semi-arboreal populations show diversification in preferences of species and positions of the tree on which they are found. Shell morphologies of M. hahajimana exhibit remarkable geographical variation, and they have a clear relationship with their life histories. The morphological variation of M. hahajimana results from adaptation to different lifestyles. The habitats of these populations influence the relationships with other species of Mandarina coexisting with M. hahajimana. This suggests that the morphological and ecological divergence within M. hahajimana has been induced by competitive interaction with other species of Mandarina. Character displacement may have played an important role in promoting adaptive radiation of Mandarina in the Bonin Islands.