Data and code from: Age-related trends in niche position and specialization in neotropical vertebrates

Species’ niche positions and breadths within a region’s environmental
space, measured through Ecological Niche Factor Analysis (ENFA) as
marginality and specialization, can reflect evolutionary constraints
related to lineage age. The “Internal incumbency” hypothesis predicts that
older species, due to competitive preemption, occupy more central niche
positions than younger ones. In addition, regarding specialization, there
are two contrasting predictions: the "Time-and-specialization"
hypothesis posits that older species are more specialized given that they
had more time to adapt to an environment, whereas the
"Resource-use" hypothesis proposes that younger species are more
specialized due to occupying narrower ecological niches, which may drive
higher speciation and extinction rates. This study explores the
relationship between species age and their climatic niche position and
specialization among Neotropical terrestrial vertebrates. Using ENFA, we
estimated the marginality (niche position) and specialization (niche
breadth) of 1175 mammals, 3001 birds, 1826 reptiles, and 1435 amphibians
across the Neotropical biomes occupied by each species. Phylogenetic
generalized least squares (PGLS) models were used to analyze the
relationships between species age, marginality, and specialization across
vertebrate classes. Although regression coefficients were predominantly
negative, suggesting that older species tend to occupy more central niche
positions and exhibit lower specialization, the explanatory power of the
models was extremely low. Taken together, the consistently negligible
variance explained across taxa and biomes indicates that species age is
not a general driver of niche position and specialization, contrary to the
expectations articulated in our hypotheses.