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Exposed and isolated alpine ecosystems present evolutionary challenges for flying species worldwide. Many insects have undergone dramatic wing reduction in response to these harsh conditions, losing the ability to fly. By contrast, some taxa have countered alpine conditions by evolving larger wings to improve flight ability. In this study, we investigated how two independent clades of Zelandoperla fenestrata stoneflies respond to upland environments. Our results revealed strikingly different adaptations to elevation across the two closely related clades. In Clade 1 (southern South Island), wing length decreases sharply with increasing elevation. In contrast, wing length in the geographically adjacent Clade 2 (northern South Island, and North Island) increases with elevation. These contrasting strategies highlight the diverse adaptive pathways that may exist even for closely related lineages encountering similar environmental challenges. [ABSTRACT FROM AUTHOR]

Many hypotheses in the field of phylogenetic comparative biology involve specific changes in the rate or process of trait evolution. This is particularly true of approaches designed to connect macroevolutionary pattern to microevolutionary process. We present a method to test whether the rate of evolution of a discrete character has changed in one or more clades, lineages, or time periods. This method differs from other related approaches (such as the "covarion" model) in that the "regimes" in which the rate or process is postulated to have changed are specified a priori by the user, rather than inferred from the data. Similarly, it differs from methods designed to model a correlation between two binary traits in that the regimes mapped onto the tree are fixed. We apply our method to investigate the rate of dewlap colour and/or caudal vertebra number evolution in Caribbean and mainland clades of the diverse lizard genus Anolis. We find little evidence to support any difference in the evolutionary process between mainland and island evolution for either character. We also examine the statistical properties of the method more generally and show that it has acceptable type I error, parameter estimation, and power. Finally, we discuss some general issues of frequentist hypothesis testing and model adequacy, as well as the relationship of our method to existing models of heterogeneity in the rate of discrete character evolution on phylogenies. [ABSTRACT FROM AUTHOR]

Depth gradients in lakes are often key drivers of population divergence and speciation in fishes. New Zealand has many deep lakes but no known profundal specialist fishes or cases of intralacustrine speciation. We sampled a native benthic fish, the common bully (Gobiomorphus cotidianus), from 5 to 90 m depth in four South Island lakes to test for morphological, ecological, or genetic differentiation associated with depth. Deeper fish consistently had narrower bodies, while other morphological traits showed variable relationships with depth. Carbon and nitrogen stable isotope values of fish increased with depth, largely tracking isotopic trends with depth of benthic invertebrate prey. Genotyping-by-sequencing showed some genome-wide differentiation between two of the lakes, but no evidence for within-lake genetic structuring along depth gradients. These results indicate that individual bullies associate with shallower or deeper habitats within their lifetimes, but we found no evidence of progress toward genetic divergence within lakes. The apparent lack of intralacustrine genetic divergence in New Zealand's fishes may be explained by a combination of environmental factors and constraints intrinsic to its marine-derived freshwater fish fauna. Les gradients de profondeur dans les lacs sont souvent des facteurs cles de divergence des populations et de speciation chez les poissons. La Nouvelle-Zelande compte de nombreux lacs profonds, mais aucun poisson specialiste des profondeurs, ni cas de speciation intralacustre. Nous avons echantillonne un poisson benthique indigene, Gobiomorphus cotidianus, a des profondeurs allant de 5 a 90 m dans quatre lacs de l'lle du Sud, afin de verifier s'il presentait une differenciation morphologique, ecologique ou genetique associee a la profondeur. Les poissons preleves a de plus grandes profondeurs etaient uniformement caracterises par des corps plus etroits, alors que d'autres caracteres morphologiques presentaient des relations variables avec la profondeur. Les valeurs d'isotopes stables de carbone et d'azote des poissons augmentaient avec la profondeur, suivant generalement les tendances isotopiques en fonction de la profondeur de proies invertebrees benthiques. Le genotypage par sequenqage a fait ressortir une certaine differenciation a l'echelle du genome entre deux des lacs, mais aucun indice de structuration genetique a l'interieur d'un meme lac le long de gradients de profondeur. Ces resultats indiquent que des G. cotidianus sont tour a tour associes a des habitats de faible profondeur et de plus grande profondeur au cours de leur vie, mais aucun indice d'une progression vers une divergence genetique a l'interieur d'un meme n'a ete releve. L'apparente absence de divergence genetique intralacustre chez des poissons neo-zelandais pourrait s'expliquer par une combinaison de facteurs environnementaux et de contraintes intrinseques a la faune de poissons d'eau douce derives de poissons marins de Nouvelle-Zelande. [Traduit par la Redaction], Introduction Environmental gradients are important regulators of biodiversity, contributing to community turnover, population structure, and long-term evolutionary diversification (Doebeli and Dieckmann 2003; Seehausen et al. 2008). Water depth is a [...]

Sea level rise threatens ecosystem function in coastal lakes by increasing salinity and altering community composition. As mobile generalists, fish have considerable influence on the stability of a system by impacting trophic network structure. Understanding their diet across abiotic gradients, including salinity, can show key characteristics of their ecological role, and predator diet shifts may serve as warning signs of food web restructuring. Stomach contents analysis was used to look at the diet of Retropinna retropinna (common smelt) across shallow coastal lakes on Rēkohu (Chatham Island). Smelt diets from 10 lakes (seven freshwater; three salt-influenced) were analysed. Comparisons of salt-influenced and freshwater lakes showed shifts in composition. Smelt in freshwater lakes predominantly consumed herbivorous, omnivorous, or predatory insect larvae while diet in salt-influenced lakes was dominanted by crustacean shredders. Population diet varied somewhat less among salt-influenced lakes than among freshwater lakes, suggesting homogenisation of smelt diet with salinity. Differences in composition and heterogeneity did not translate to consistent differences in total niche width or individual specialisation between freshwater and salt-influenced lakes. Further development of knowledge on biological structure across salinity gradients is essential to understand ecosystem function under future climate scenarios. [ABSTRACT FROM AUTHOR]

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