Contrasting size-dependent life history strategies of an insular lizard

Abstract

In many species with continuous growth, body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures. We developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history tactics. For each population, we broke down differences in population growth rates into contributions from size-dependent body growth, survival, and fecundity. A life table response experiment (LTRE) was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate (λ). Perturbation analyses revealed that the largest adults contributed the most to the population growth rate, but this was not true in the population with the smallest adults and size-independent fertility. Although we were not able to identify a single factor responsible for this difference, the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival, individual body growth, and fertility. Our results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.

Insular holobionts: persistence and seasonal plasticity of the Balearic wall lizard (Podarcis lilfordi) gut microbiota

“…However, these two islets show clear differences in their morphological and life history traits (smaller body size and marked senescence in NG, Rotger et al 2020), indicating an ongoing process of divergence between the two islets (Rotger et al, 2020(Rotger et al, , 2021. Their closed microbiota similarity and divergence from the the islet EC might still be compatible with a process of codivergence of microbes with the host over time, as observed in several instances across the animal kingdom (Lim & Bordenstein, 2020;Mallott & Amato, 2021).…”

“…The reproduction period is extended from Spring to the end of the Summer. Animals begin to lay eggs in May and females can lay two to three clutches (Castilla & Bauwens, 2000), usually of two to four eggs (Rotger et al, 2020). All specimens were caught in georeferenced pitfall traps containing sterile fruit juices placed along paths and vegetation edges.…”

“…This transition in the trophic niche is particularly strong between spring (with the highest resource availability) and autumn (lowest), with hot summers marking a progressive limitation of resource availability (Pérez-Cembranos et al, 2016). According to a recent study based on individual fecal content analysis in NM and NG, the P. lilfordi seasonal response is sex specific (Santamaría et al, 2019), and particularly noticeable in autumn, when food resources are scarce and males show a despotic behavior (Rotger et al, 2020), restricting the female niche amplitude (Santamaría et al, 2019). Despite a sex influence on both lizard metabolism and trophic niche behavior (Pérez-Mellado et al, 2015), males and females did not carry distinct gut microbiotas in any of the three islets, nor were microbial differences observed between sexes within a season (season-by-sex interaction was not significant for individual islets).…”

“…In the present study we focused on three well-studied populations of Lilford's wall lizard found in three close islets south of Mallorca: Na Moltona, Na Guardis and En Curt (Figure 1). The three islets are less than five km apart, share nearly the same Mediterranean climate and biotic environment, and differ primarily in size and biotic index (Rotger et al, 2020). In particular, the smallest islet (En Curt) hosts a reduced plant community compared to the other two islets (Rotger et al, 2021).…”

“…Since 2010, the three populations have been under a demographic study: every spring and autumn, individuals are sampled through a capture and recapture method, photo-identified by digitally recording the pattern of ventral scales (Moya et al, 2015), sexed and measured (i.e., body length and weight). This has provided important individuallevel and longitudinal data for each population, showing that the three populations differ in demographic parameters and life history traits such as body growth rate, fecundity, survival, and density (Rotger et al, 2016(Rotger et al, , 2020. A recent genetic study based on microsatellites indicates that the three populations diverged about 5,000 -8,000 years ago (with no recent relevant immigration events), and that Na Moltona and Na Guardis represent closer sister populations (Rotger et al, 2021).…”