Latitude Matters: A Global Perspective on Climate-Driven Demographic Responses in Tarantulas
ABSTRACT
Aim
To investigate how past climate change has shaped the genetic diversity and demographic responses (changes in population size and structure inferred from genetic data) of tarantulas across latitudes, and to test whether climate–demography relationships vary with latitude.
Location
Global; spanning tropical to temperate regions.
Taxon
Tarantulas (family Theraphosidae).
Methods
We compiled mitochondrial cytochrome oxidase I (COI) sequences for 50 tarantula species worldwide, including newly generated sequences, to estimate nucleotide diversity (π) and Tajima's D as indicators of genetic diversity and population demographic history. Ecological niche models (ENMs) were constructed under present-day and Last Glacial Maximum (LGM) climatic conditions to quantify changes in habitat suitability since the LGM. Using generalised linear models (GLMs), we tested associations between latitude, habitat suitability change and genetic metrics.
Results
Pairwise correlations among latitude, habitat suitability change and genetic metrics showed no significant associations. However, GLMs revealed a significant interaction: the effect of habitat suitability change on Tajima's D was strongly positive at high latitudes but negative or negligible at low latitudes. This indicates that demographic responses to past climate change varied latitudinally. Several high-latitude species showed genetic signatures of demographic expansion and range increase since the LGM.
Main Conclusions
Our results support the hypothesis that species at higher latitudes experience stronger demographic fluctuations due to historical climate change, aligning with Darwin's predictions. Moreover, patterns of demographic growth in temperate taxa suggest that some species may benefit from recent warming, consistent with Janzen's climatic variability hypothesis. These findings demonstrate that climate-driven genetic and demographic responses in tarantulas are probably shaped by latitude, highlighting the importance of integrating population genetics with ecological niche modelling to understand species' resilience under climate change.
Biswas, A., & Karanth, P. Latitude Matters: A Global Perspective on Climate-Driven Demographic Responses in Tarantulas. Journal of Biogeography, e70055. https://doi.org/10.1111/jbi.70055