Macroecology and the evolution of complex maternal care in Embioptera

Biodiversity in the tropics is known to be more complex. That complexity includes greater predation and parasite pressure, according to E. O. Wilson and many other ecologists. Recently, a paper by Santos et al. (2017) found that parental care in arthropods is more complex and  more necessary in regions with higher humidity and constant, warm temperatures. The authors’ measure of seasonality or lack thereof was annual evapotranspiration (AET).  We sought to apply a similar analysis to the order Embioptera. This study is the first attempt to explore diversity of one of the key characteristics of Embioptera: maternal care of eggs.  Our sample includes 28 species from regions ranging from Australia to SE Asia, South and Central America, USA, the Mediterranean and Africa. We scored egg handling treatments such as how the individual eggs are covered or not at all, aligned or not, affixed or not, coated with silk or not, and so forth. We found that, as seen for arthropods in general, embiopterans showed more complex egg handling where the climate is constant and primary productivity and predation threats remain high. Increasing complexity of egg handling was positively and significantly related to increasing AET. Phylogenetic signal for a composite measure of maternal care was also significant, contributing to diversity in maternal care of eggs.