Sexual size dimorphism and Rensch's rule in Canidae

The size variation between males and females of a species is a phenomenon known as sexual size dimorphism (SSD). The observed patterns of variation in SSD among species has led to the formulation of Rensch's rule, which establishes that, in species showing a male size bias, SSD increases with an increase in the body size of the species. However, for species in which there is a female size bias, the SSD would decrease when the body size of the species increases. In the present study, we examined the variation in body size and SSD of 33 species of canids from estimates of body mass and body length. We studied its relationship with life‐history characteristics and tested Rensch's rule using phylogenetic generalized least squares and phylogenetic reduced major axis regressions, respectively. We observed the existence of correlation between body mass and body length, although the SSDs from these estimators are uncorrelated. SSD did not show the pattern predicted by Rensch's rule. SSD also did not show any correlation with life‐history traits. It is likely that the low SSD observed in canids is related to the monogamy observed in the family, which is a rare situation in mammals.     

On the evolution and diversification of an Andean clade of reptiles: combining morphology and DNA sequences of the palluma group (Liolaemidae: Phymaturus)

Phymaturus comprises 44 species mainly distributed along the south‐west of South America on both sides of the Andes. In this study we present a phylogenetic analysis of Phymaturus of the palluma group, one of its two large clades, including almost all described species. This analysis duplicates the number of in‐group taxa compared with previous contributions. We performed a total‐evidence analysis, combining molecular and morphological characters: sequencing fragments of cytochome b (cytb), 12S, and ND4, for all terminals; describing 45 new morphological characters; and incorporating all DNA sequences available from GenBank. Separate analyses of morphology and DNA partitions are presented and discussed in detail. Seven subclades are recognized here. We named three new subclades and redefined another, found to be paraphyletic. In order to recognize lineages within the traditional Phymaturus palluma group we proposed to treat it as a natural group, containing within it the ranks of clade, subclade, and lineages, respectively. The palluma group is composed by the vociferator and the bibronii clades. The vociferator clade, composed of Chilean and Argentinean species, would be the most basal in the group. Within the bibronii clade, the roigorum subclade includes the Phymaturus verdugo lineage, whereas the mallimaccii subclade would consist of 13 terminal taxa, for which three Chilean species have been added. In this study, morphological apomorphies are identified for all clades and the evolution of ‘male head melanism’ is discussed. © 2015 The Linnean Society of London     

CO2 Saturation and Trophic Shift Induced by Microbial Metabolic Processes in a River-Dominated Ocean Margin (Tropical Shallow Lagoon,Chilika, India)

An effort has been made for the first time in Asia's largest brackish water lagoon, Chilika, to investigate the spatio-temporal variability in primary productivity (PP), bacterial productivity (BP), bacterial abundance (BA), bacterial respiration (BR) and bacterial growth efficiency (BGE) in relation to partial pressure of CO₂ (pCO₂) and CO₂ air–water flux and the resultant trophic switchover. Annually, PP ranged between 24 and 376 µg C L^?1 d^?1 with significantly low values throughout the monsoon (MN), caused by light limitation due to inputs of riverine suspended matter. On the contrary, BP and BR ranged from 11.5 to 186.3 µg C L^?1 d^?1 and from 14.1 to 389.4 µg C L^?1 d^?1, respectively, with exceptionally higher values during MN. A wide spatial and temporal variation in the lagoon trophic status was apparent from BP/PP (0.05–6.4) and PP/BR (0.10–18.2) ratios. The seasonal shift in net pelagic production from autotrophy to heterotrophy due to terrestrial organic matter inputs via rivers, enhanced the bacterial metabolism during the MN, as evident from the high pCO₂ (10,134 µatm) and CO₂ air–water flux (714 mm m^?2 d^?1). Large variability in BGE and BP/PP ratios especially during MN led to high bacteria-mediated carbon fluxes which was evident from significantly high bacterial carbon demand (BCD >100% of PP) during this season. This suggested that the net amount of organic carbon (either dissolved or particulate form) synthesized by primary producers in the lagoon was not sufficient to satisfy the bacterial carbon requirements. Lagoon sustained low to moderate autotrophic–heterotrophic coupling with annual mean BCD of 231% relative to the primary production, which depicted that bacterioplankton are the mainstay of the lagoon biogeochemical cycles and principal players that bring changes in trophic status. Study disclosed that the high CO₂ supersaturation and oxygen undersaturation during MN was attributed to the increased heterotrophic respiration (in excess of PP) fuelled by allochthonous organic matter. On a spatial scale, lagoon sectors such as south sector, central sector and outer channel recorded “net autotrophic,” while the northern sector showed “net heterotrophic” throughout the study period.     

不同地位克氏原螯虾胜利者-失败者效应的稳定性

为探究不同地位的克氏原螯虾(Procambarus clakii)胜利者-失败者效应的稳定性。通过视频拍摄优势者和从属者在新的领域中各自与等重量级雄性螯虾连续遭遇战,统计胜负场数、格斗次数、时间、优势指数等多个参数。在与陌生对手的首次交战中,40个优势者中有23只螯虾取得了胜利,17只失败,胜负比例之间差异不显著;而从属者中获胜比例为18/40,与失败者的比例之间也没有差异,说明优势者和从属者之间原有的等级地位并不被陌生对手识别。在与陌生对手的第二次交战中,获胜的优势者中18/23的螯虾再次胜利,极显著高于失败的螯虾比例;获胜的从属者中,仅11/18的螯虾再次胜利,与失败者的比例之间不显著;而失败的优势者中,13/17的螯虾持续失败,失败的从属者中,17/22的螯虾持续失败,均显著高于获胜的比例,说明不同地位的螯虾胜利者-失败者效应稳定性不同,优势者的胜利者-失败者效应均比较稳定,而从属者的失败者效应稳定,胜利者效应并不稳定,一胜之后不能获得稳定、完全的二胜。对格斗次数、时间、优势指数等参数统计分析发现,胜利或失败的优势者以及从属者在格斗策略上有较大的差异。     

How reticulated are species?

Many groups of closely related species have reticulate phylogenies. Recent genomic analyses are showing this in many insects and vertebrates, as well as in microbes and plants. In microbes, lateral gene transfer is the dominant process that spoils strictly tree‐like phylogenies, but in multicellular eukaryotes hybridization and introgression among related species is probably more important. Because many species, including the ancestors of ancient major lineages, seem to evolve rapidly in adaptive radiations, some sexual compatibility may exist among them. Introgression and reticulation can thereby affect all parts of the tree of life, not just the recent species at the tips. Our understanding of adaptive evolution, speciation, phylogenetics, and comparative biology must adapt to these mostly recent findings. Introgression has important practical implications as well, not least for the management of genetically modified organisms in pest and disease control.     

Translating niche features: Modelling differential exposure of Argentine reptiles to global climate change

Global climate change affects the distributions of ectotherms and may be the cause of several conservation problems, such as great displacement of climatic suitable spaces for species and, consequently, important reductions of the extent of liveable places, threatening the existence of many of them. Species exposure (and hence vulnerability) to global climate change is linked to features of their climatic niches (such as the relative position of the inhabited localities of each species in the climatic space), and therefore to characteristics of their geographic ranges (such as the extent of the distributions or altitudinal range inhabited by the species). In order to analyze the pattern of response of Argentine reptiles to global climate change, we ran phylogenetic generalized least squares models using species exposure to global climate change as a response variable, and (i) niche properties (breadth and position of the species in the climate space) and (ii) general features of the distribution of species (maximum latitude, altitudinal range, maximum elevation, distributional range and proximity to the most important dispersal barrier) as predictors. Our results suggest that the best way to explain climate change exposure is by combining breadth and position of climatic niche of the species or combining geographic features that are indicators of both niche characteristics. Our best model shows that in our study area, species with the narrowest distributional ranges that also inhabit the highest elevations are the most exposed to the effects of global climate change. In this sense, reptile species from Yungas, Puna and Andes ecoregions could be especially vulnerable to the effects of climate change. We believe that these types of models may represent an interesting tool for determining species and places particularly threatened by the effects of global climate change, which should be strongly considered in conservation planning.     

Introductions do not compensate for functional and phylogenetic losses following extinctions in insular bird assemblages

The ratio of species extinctions to introductions has been comparable for many insular assemblages, suggesting that introductions could have ‘compensated’ for extinctions. However, the capacity for introduced species to replace ecological roles and evolutionary history lost following extinction is unclear. We investigated changes in bird functional and phylogenetic diversity in the wake of extinctions and introductions across a sample of 32 islands worldwide. We found that extinct and introduced species have comparable functional and phylogenetic alpha diversity. However, this was distributed at different positions in functional space and in the phylogeny, indicating a ‘false compensation’. Introduced and extinct species did not have equivalent functional roles nor belong to similar lineages. This makes it unlikely that novel island biotas composed of introduced taxa will be able to maintain ecological roles and represent the evolutionary histories of pre‐disturbance assemblages and highlights the importance of evaluating changes in alpha and beta diversity concurrently.     

New trophic indicators and target values for an ecosystem-based management of fisheries

In the present study, we tested five trophic indicators and we demonstrated their usefulness to assess the environmental status of marine ecosystems and to implement an ecosystem approach to fisheries management (EAFM). The tested indicators include the slope of the biomass spectrum, the mean trophic level (MTL), the marine trophic index (MTI) and two newly developed indicators, the high trophic level indicator (HTI) and the apex predator indicator (API). Indicators are compared between current state and potential reference situations, using as case studies: the Celtic Sea/Bay of Biscay, North Sea and English Channel ecosystems. Trophic spectra are obtained from Ecopath models while reference situations are estimated, simulating with EcoTroph and Ecosim different fishing pressures including three candidate scenarios for an EAFM. Inter-ecosystems assessments are done using Ecopath models, simulations outputs and scientific surveys data to assess the current states of the studied ecosystems, contrast the reference situations and analyze the responses of all indicators. Sensitivity analyses are also conducted on the main simulation parameters to test the robustness of the chosen indicators. Ecosystems specific targets for EAFM are proposed for the five trophic indicators estimated from whole-ecosystem models, while in the Celtic Sea/Bay of Biscay ecosystem targets are proposed for the MTL (=3.85) and HTI (48%) estimated from standard bottom-trawl surveys. The HTI is proposed to be relevant for survey data and the API is recommended using whole-ecosystem models. We conclude that HTI and API show trends in ecosystems health better than MTI.