The “resource availability hypothesis” predicts occurrence of larger rodents in more productive habitats. This prediction was tested in a dataset of 1,301 rodent species. We used adult body mass as a measure of body size and normalized difference vegetation index (NDVI) as a measure of habitat productivity. We utilized a cross-species approach to investigate the association between these variables. This was done at both the order level (Rodentia) and at narrower taxonomic scales. We applied phylogenetic generalized least squares (PGLS) to correct for phylogenetic relationships. The relationship between body mas and NDVI was also investigated across rodent assemblages. We controlled for spatial autocorrelation using generalized least squares (GLS) analysis. The cross-species approach found extremely low support for the resource availability hypothesis. This was reflected by a weak positive association between body mass and NDVI at the order level. We find a positive association in only a minority of rodent subtaxa. The best fit GLS model detected no significant association between body mass and NDVI across assemblages. Thus, our results do not support the view that resource availability plays a major role in explaining geographic variation in rodent body size.
Over the last few years, a debate about the relative roles of distinct factors on the evolution of lineages has gained prominence. The family Canidae is an excellent group for exploring this idea, owing to its rich fossil history. One of the most intriguing traits in canids is social organization, which varies from highly social to solitary species. However, we do not have a complete understanding of how sociality evolved in this clade. Here, we use a combination of phylogenetic analyses, ancestral character reconstructions and comparative methods on the only extant subfamily, Caninae, to understand how traits expressing ecological features evolved over the last 12.6 Myr. Our findings suggest that the evolution of low, medium and high sociality forms was abrupt and highly correlated with the evolution of hypo-, meso- and hypercarnivorous forms, respectively. In addition, our results suggest that the evolution of phenotypic traits in Caninae occurred through a sequential cause–effect relationship, where changes in habitat use and body size probably triggered changes in social behaviour, which in turn drove the evolution of diet.
Colonization of a new environment may trigger an explosive radiation process, defined as an accelerated accumulation of species in a short period of time. However, how often colonization events trigger explosive radiations is still an open question. We studied the worldwide dispersal of the subfamily Caninae, to investigate whether the invasion of new continents resulted in explosive radiations. We used a combination of phylogenetic analyses and ancestral area reconstructions to estimate ancestral ranges of 56 extant and extinct species of Caninae, as well as variation in speciation and extinction rates through time and across clades. Our findings indicate that canids experienced an explosive radiation event when lineages were able to cross the Bering Strait and the Isthmus of Panama to reach Eurasia and South America, respectively, around 11 million years ago. This large number of species arising in a short period of time suggests that canids experienced ecological opportunity events within the new areas, implying that the differences in the ecological settings between continents may be responsible for the variation in clade dynamics. We argue that interaction with other carnivores probably also affected the diversification dynamics of canids.
Colonization of a new environment may trigger an evolutionary radiation, defined as an accelerated accumulation of species in a short period of time. However, how often colonization events trigger such radiations is still an open question. We studied the worldwide dispersal of Caninae to investigate whether the invasion of new continents resulted in elevated species diversification. We used a combination of ancestral range estimation and phylogenetic analyses to estimate the ancestral ranges of 56 extant and extinct species of Caninae, as well as variation in speciation and extinction rates through time and across clades. Our findings indicate that canids experienced an evolutionary radiation event when lineages were able to reach Eurasia and South America around 11 million years ago. A large number of species arising in a short period of time suggests that canids experienced ecological opportunity events within the new areas, implying that the differences in the ecological settings between continents, and size variation among Canidae and other carnivores may be responsible for the variation in clade dynamics. We suggest that the increase of grasslands and the new herbivorous fauna that came with it were the major forces responsible for the diversification of wolves in North America, while empty niches and the absence of competitors can explain the success of canids in Africa and South America. Interaction with other carnivores probably also affected the diversification dynamics of canids.
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