Ecological Speciation

The importance of ecologically-mediated divergent selection in accelerating trait evolution has been poorly studied in the most species-rich biome of the planet, the continental Neotropics. We performed a macroevolutionary analyses of trait divergence and diversification rates across closely-related pairs of Andean and Amazonian passerine birds, to assess whether the difference in elevational range separating species pairs – as proxy for the degree of ecological divergence – influences the speed of trait evolution and diversification rates. We found that elevational differentiation is associated with faster divergence of song frequency, a trait important for premating isolation, and several morphological traits, which may contribute to extrinsic postmating isolation. However, we found no evidence for elevational differentiation accelerating recent speciation rates, possibly due to early bursts of diversification during the uplift of the eastern Andes. Together, our results suggest that ecological differentiation may speed up trait evolution, but not diversification of Neotropical birds.

Ecological speciation occurs when adaptation to different environments or resources causes the evolution of re- productive isolation. This process is now thought to be very important in the evolution of biological diversity. Indeed, sup- port for ecological speciation is so often asserted in the literature that one can get the impression of ubiquity. Eager to ride on the coattails of

While the role of host preference in ecological speciation has been investigated extensively in terrestrial systems, very little is known in marine environments. Host preference combined with mate choice on the preferred host can lead to population subdivision and adaptation leading to host shifts. We use a phylogenetic approach based on two mitochondrial genetic markers to disentangle the taxonomic status and to investigate the role of host specificity in the speciation of the nudibranch genus Phestilla (Gastropoda, Opisthobranchia) from Guam, Palau and Hawaii. Species of the genus Phestilla complete their life cycle almost entirely on their specific host coral (species of Porites, Goniopora and Tubastrea). They reproduce on their host coral and their planktonic larvae require a host-specific chemical cue to metamorphose and settle onto their host. The phylogenetic trees of the combined cytochrome oxidase I and ribosomal 16S gene sequences clarify the relationship among species of ...

Reproductive strategies of closely related species distributed along successional gradients should differ as a consequence of the trade-off between competition and colonization abilities. We compared male reproductive strategies of Quercus robur and Q. petraea, two partly interfertile European oak species with different successional status. In the studied even-aged stand, trees of the late-successional species (Q. petraea) grew faster and suffered less from intertree competition than trees of the earlysuccessional species (Q. robur). A large-scale paternity study and a spatially explicit individual-based mating model were used to estimate parameters of pollen production and dispersal as well as sexual barriers between species. Male fecundity was found to be dependent both on a tree’s circumference and on its environment, particularly so for Q. petraea. Pollen dispersal was greater and more isotropic in Q. robur than in Q. petraea. Premating barriers to hybridization were strong in both species, but more so in Q. petraea than in Q. robur. Hence, predictions based on the competition–colonization trade-off are well supported, whereas the sexual barriers themselves seem to be shaped by colonization dynamics.