From micro-to macroevolution:brood parasitism as a driver of phenotypic diversity in birds

A fun dame ntal question in biology is how diversity evolves and why some clades are more diverse than others.Phenotypic diversity has often been shown to result from morphological adaptation to different habitats.The role of behavioral interactions as a driver of broadscale phenotypic diversity has received comparatively less attention.Behavioral interactions,however,are a key agent of natural selection.Antagonistic behavioral interactions with predators or with parasites can have significant fitness consequences,and hence act as strong evolutionary forces on the phe no type of species,ultimately gen erating diversity betwee n species of both victims and exploiters.Avian obligate brood parasites lay their eggs in the nests of other species,their hosts,and this behavioral interaction between hosts and parasites is often considered one of the best examples of coevolution in the natural world.In this review,we use the coevolution between brood parasites and their hosts to illustrate the potential of behavioral interactions to drive evolution of phenotypic diversity at different taxonomic scales.We provide a bridge between behavioral ecology and macroevolution by describing how this interaction has increased avian phenotypic diversity not only in the brood parasitic clades but also in their hosts.

Monsoon boosted radiation of the endemic East Asian carps

Major historical events often trigger the rapid flourishing of a few lineages,which in turn shape established biodiversity patterns.How did this process occur and develop?This study provides a window into this issue.The endemic East Asian carps(EEAC)dominated the ichthyofauna of East Asia and exhibited a high degree of adaptation to monsoonal river-lake ecosystems.A series of evidence,including ecogeography,phylogenetics,and macroevolution,suggests that the EEAC is a lineage that arose with the East Asian monsoon and thrived intimately with subsequent monsoon activities.We further deduce the evolution of the EEAC and find that a range of historical events in the monsoon setting(e.g.,marine transgression and regression and glacial-interglacial cycle)have further reshaped the distribution patterns of EEAC’s members.Comparative genomics analyses reveal that introgressions during the initial period of EEAC radiation and innovations in the regulation of the brain and nervous system may have aided their adaptation to river-lake ecosystems in a monsoon setting,which boosted radiation.Overall,this study strengthens knowledge of the evolutionary patterns of freshwater fishes in East Asia and provides a model case for understanding the impact of major historical events on the evolution of biota.

Functional correlates of skull shape in Chiroptera:feeding and echolocation adaptations

Morphological,functional,and behavioral adaptations of bats are among the most diverse within mammals.A strong association between bat skull morphology and feeding behavior has been suggested previously.However,morphological variation related to other drivers of adaptation,in particular echolocation,remains understudied.We assessed variation in skull morphology with respect to ecology(diet and emission type)and function(bite force,masticatory muscles and echolocation characteristics)using geometric morphometrics and comparative methods.Our study suggests that variation in skull shape of 10 bat families is the result of adaptations to broad dietary categories and sound emission types(oral or nasal).Skull shape correlates with echolocation parameters only in a subsample of insectivorous species,possibly because they(almost)entirely rely on this sensory system for locating and capturing prey.Insectivores emitting low frequencies are characterized by a ventrally tilted rostrum,a trait not associated with feeding parameters.This result questions the validity of a trade-off between feeding and echolocation function.Our study advances understanding of the relationship between skull morphology and specific features of echolocation and suggests that evolutionary constraints due to echolocation may differ between different groups within the Chiroptera.

How do small birds evolve in response to climate change?Data from the long-term record at La Brea tar pits

Biology textbooks describe the small changes in the beaks of the Galápagos finches as exemplars of how birds evolve in response to environmental changes.However,recent studies of the abundant fossil birds at Rancho La Brea find no evidence of evolutionary responses to the dramatic climate changes of the glacial–interglacial cycle over the past 35000 years:none of the large birds exhibit any change in body size or limb proportions,even during the last glacial maximum approximately 18000–20000 years ago,when the southern California chaparral was replaced by snowy coniferous forests.However,these are all large birds with large ranges and broad habitat preferences,capable of living in many different environments.Perhaps the smaller birds at La Brea,which have smaller home ranges and narrower habitats,might respond to climate more like Galápagos finches.The only 3 common small birds at La Brea are the western meadowlark,the yellow-billed magpie and the raven.In this study,we demonstrate that these birds also show complete stasis over the last glacial–interglacial cycle,with no statistically significant changes between dated pits.Recent research suggests that the small-scale changes over short timescales seen in the Galápagos finches are merely fluctuations around a stable morphology,and rarely lead to long-term accumulation of changes or speciation.Instead,the prevalence of stasis supports the view that long-term directional changes in morphology are quite rare.While directional changes in morphology occur frequently over short(<1 ka)timescales,in the long term such changes only rarely remain stable for long enough to appear in the fossil record.

Hematological parameters of a Neotropical wild frog population,with a phylogenetic perspective on blood cell composition in Anura

Hematological parameters can provide key information to an animal health status.However,this information is usually hard to obtain.Here,we described the hematological parameters of Leptodactylus podicipinus in the Brazilian Pantanal.We measured red blood cell morphometrics,erythrogram,and leukogram.We also tested for phylogenetic signal in the erythrogram and leukogram of 48 frog species from 15 families,testing if body size explains their variation.Lymphocytes were the most abundant leukocytes(>60%)in L.podicipinus,followed by neutrophils(∼10%).Given that L.podicipinus is an abundant and widely distributed species in central Brazil,knowing its hematological pattern can help establish a baseline and improve its use as a bioindicator of environmental degradation.Mean corpuscular hemoglobin and value contributed more to the phylomorphospace of erythrogram,in which Leptodactylus spp.and Hypsiboas raniceps had lower values of these variables,whereas Bufotes viridis and Hyla arborea had high values.The phylogenetic signal was spread throughout the dimensions of the leukogram phylomorphospace.The variables that most contributed to it were total leukocytes counts,lymphocytes,and neutrophils.We also found a moderate phylogenetic signal for both the erythrogram and leukogram.Accordingly,body size accounted for a low proportion of variation in both the leukogram(4.7%)and erythrogram(0.57%).By applying phylogenetic comparative methods to hematological parameters,our results add a new perspective on the evolution of blood cell physiology in frogs.

Selection for Cheaper Amino Acids Drives Nucleotide Usage at the Start of Translation in Eukaryotic Genes

Coding regions have complex interactions among multiple selective forces,which are manifested as biases in nucleotide composition.Previous studies have revealed a decreasing GC gradient from the 5′-end to 3′-end of coding regions in various organisms.We confirmed that this gradient is universal in eukaryotic genes,but the decrease only starts from the~25th codon.This trend is mostly found in nonsynonymous(ns)sites at which the GC gradient is universal across the eukaryotic genome.Increased GC contents at ns sites result in cheaper amino acids,indicating a universal selection for energy efficiency toward the N-termini of encoded proteins.Within a genome,the decreasing GC gradient is intensified from lowly to highly expressed genes(more and more protein products),further supporting this hypothesis.This reveals a conserved selective constraint for cheaper amino acids at the translation start that drives the increased GC contents at ns sites.Elevated GC contents can facilitate transcription but result in a more stable local secondary structure around the start codon and subsequently impede translation initiation.Conversely,the GC gradients at four-fold and two-fold synonymous sites vary across species.They could decrease or increase,suggesting different constraints acting at the GC contents of different codon sites in different species.This study reveals that the overall GC contents at the translation start are consequences of complex interactions among several major biological processes that shape the nucleotide sequences,especially efficient energy usage.

Does the diversification rate of endemic birds of China's Mainland follow abrupt,gradual shifting or constant patterns?

In this brief report,time-varying(including both gradual and abrupt change)and time-constant diversification models are fitted on a phylogeny of endemic birds of China's Mainland to test the diversification patterns of endemic birds in the region.The results show that phylogeny of endemic birds is best quantified by a constant-rate diversification model through model comparison.Limitations of the study are discussed.In particular,ignorance of non-endemic taxa and the limited sampling of endemic taxa could influence the conclusions of the study.