Abstract
In social animals, group prey capture could facilitate colonization of new areas with low resource availability. Parawixia bistriata is a colonial spider inhabiting seasonal dry forests and mesic habitats in South America. Individuals capture prey as a group, which allows individuals to broaden their foraging niche by incorporating large prey that cannot be subdued in solitary captures. P. bistriata exhibits two behavioural ecotypes a “dry” (plastic) ecotype which modifies individual’s tendency to capture prey in a group depending on food resources and a “wet” (fixed) ecotype, whose tendency to group prey capture is only modulated by the size of the prey but not by prey availability. By reconstructing the range expansion of the species using phylogeographic and species distribution modelling techniques, we indirectly examined whether group prey capture could have helped P. bistriata in colonization of low resource habitats. Based on cytochrome c oxidase subunit I gene genealogy, we found older populations in northern Cerrado in Brazil with more recent populations located further south in Dry and Humid Chaco in Argentina, with the latter being the most derived. Species distribution modelling for each ecotype suggests that suitable habitat for each ecotype started to overlap at some point during the Last Glacial Maximum (21 ky BP). These results suggest that P. bistriata expanded from northern Cerrado south to the Gran Chaco, being able to colonize mesic habitats at a later stage when individuals reached southern territories in the Chaco. This evidence is opposite to the idea that GPC facilitated P. bistriata colonization from mesic to harsher environments. However, plasticity in group prey capture could have been important to allow individuals to establish in mesic habitats by reducing the cost of group capture when under high resource levels.
Highlights
There are certain behavioural traits that can facilitate colonization of a new environment by a species (Sol et al 2002; Duckworth and Badyaev 2007)
Because behavioural ecotypes are associated with different habitats and we wanted to use Species Distribution Modelling (SDM) as an independent approach for testing directional expansion of P. bistriata between habitat types, we modelled the distribution of each ecotype separately, based on the actual occurrence of populations in dry (Cerrado and Dry Chaco) and wet (Humid Chaco) habitats
Using indirect approaches by reconstructing the range expansion of P. bistriata and the paleo and current distribution of ecological niches of dry and wet ecotypes, we provided information that serves to indirectly examine the relevance of expression of group prey capture (GPC) on colo‐ nization of new habitats
Summary
There are certain behavioural traits that can facilitate colonization of a new environment by a species (Sol et al 2002; Duckworth and Badyaev 2007). Interactions with conspecifics dur‐ ing GPC can sometimes be aggressive, implying costs to individuals participating in GPC (Grinsted and Lubin 2019) Plasticity in this behaviour may be an advan‐ tage in habitats with low and more variable prey availability, whereas lack of plasticity in GPC expression is not detrimental in habitats with high and more stable prey levels. One in which this species originated and evolved in habitats with high prey conditions and the expression of GPC favoured the colonization of habitats with harsher conditions; and the other, in which P. bistriata originated in low prey condition environments with the flexible expression of GPC and later colonized high prey habi‐ tats with a later loss of behavioural flexibility in GPC that might have been favoured by the high prey levels and higher costs of aggressive interactions during GPC or by stochastic events (Lubin 1974; Fernández Campón 2007; Yip et al 2017; Quero et al 2020). Under the second scenario, we would expect the populations from mesic habitats to be more derived than those from arid environments
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