Macro-evolutionary patterns of East Asian opsariichthyin-xenocyprinin-cultrin fishes related to the formation of river and river-lake environments under monsoon climate

Although the East Asian monsoon is believed to be an important driver for the origin and evolution of the biotas in this region,the association has rarely been rigorously tested.Here,using phylogenetic comparative methods and analyses of key innovations of adaptive traits,we investigated evolutionary patterns of the East Asian cyprinid opsariichthyin-xenocyprinin-cultrin clade;the dominant species in lakes and rivers,which are the typical productions of monsoon climate.Our molecular phylogenetic analyses revealed the relationships as(Opsariichthystribe t(((Oxygaster-tribe t Aphyocypris-tribe)t Metzia-tribe)t(Paralaubuca-tribe t(Squaliobarbus-tribe t(Hypophthalmichthys-tribe t(xenocyprinins t cultrins)))))).Based on Bayesian relaxed-clock methods,we found that origins of the Squaliobarbus-and Hypophthalmichthys-tribes bearing the key adaptation of riverine spawning with drifting eggs occurred 22.5 and 21.1 Mya,respectively.These times are consistent with the Early Miocene origin of major rivers(e.g.,Yangtze River)and the appearance of the East Asian monsoon climate.Diversification of the cultrins,characterized by spawning of adhesive eggs as well as swimming and feeding in lentic waters,were estimated to have evolved 16.6 to 0.2 Mya.This period covers three phases of enhancement of the East Asian monsoon from the Middle Miocene to the Pliocene(around 15–13,10–7,and 3.5 Mya).The habitats of these cultrins and their evolution also suggest the appearance and development of a lake-river environment during those periods.Therefore,our results suggest close relationships between the evolution of these fishes and geological events in East Asia.Further,they provide knowledge that may help facilitate future conservation strategies such as the maintenance of high river flows during dam construction and operation.

Functional diversity of small-mammal postcrania is linked to both substrate preference and body size

Selective pressures favor morphologies that are adapted to distinct ecologies,resulting in trait partition!ng among ecomorphotypes.However,the effects of these selective pressures vary across taxa,especially because morphology is also influenced by factors such as phylogeny,body size,and functional trade-offs.In this study,we examine how these factors impact functional diversification in mammals.It has been proposed that trait partitioning among mammalian ecomorphotypes is less pronoun ced at small body sizes due to biomecha nical,energetic,and environ mental factors that favor a"generalist"body plan,whereas larger taxa exhibit more substantial functional adaptations.We title this the Diverge nee Hypothesis(DH)because it predicts greater morphological divergence among ecomorphotypes at larger body sizes.We test DH by using phylogenetic comparative methods to examine the postcranial skeletons of 129 species of taxonomically diverse,small-tomedium-sized(<15 kg)mammals,which we categorize as either"tree-dwellers"or"ground-dwellers."In some analyses,the morphologies of ground-dwellers and tree-dwellers suggest greater between-group differentiation at larger sizes,providing some evidence for DH.However,this trend is n either particularly strong nor supported by all an alyses.In stead,a more pronoun ced patter n emerges that is distinct from the predictions of DH:within-group phenotypic disparity increases with body size in both ground-dwellers and tree-dwellers,driven by morphological outliers among"medium'-sized mammals.Thus,evolutionary increases in body size are more closely linked to increases in within-locomotor-group disparity tha n to in creases in betwee n-group disparity.We discuss biomechanical and ecological factors that may drive these evolutionary patter ns,and we emphasize the significant evolutionary influences of ecology and body size on phenotypic diversity.

Sexual dimorphism in cranial shape and size in geomyoid rodents:multivariate and evolutionary perspectives

Geomyoid rodents provide a great study system for the analysis of sexual dimorphism.They are polygynic and many inhabit harsh arid environments thought to promote sexual dimorphism.In fact,there has been extensive work published on the sexual size dimorphism of individual populations and species within this rodent clade.However,little work has been undertaken to assess the evolutionary patterns and processes associated with this sexual dimorphism.We use multivariate analyses of cranial measurements in a phylogenetic framework to determine the distribution of size and shape dimorphism among geomyoids and test for Rensch’s rule.Our results suggest that sexual dimorphism is more common in geomyids than heteromyids,but it is not in fact universal.There is evidence for variation in sexual dimorphism across populations.Additionally,in many taxa,geographic variation appears to overwhelm existing sexual dimorphism.We find support for the repeated independent evolution of shape and size dimorphism across geomyoid taxa,but we do not find support for an association between size and shape dimorphism.There is no evidence for Rensch’s rule in geomyoids,whether at the superfamily or family level.Together,our findings suggest that there is no single explanation for the evolution of sexual dimorphism in geomyoids and that,instead,it is the product of numerous evolutionary events.Future studies incorporating phylogenetic relationships will be necessary to paint a more complete picture of the evolution of sexual dimorphism in geomyoids.