The fast‐slow life‐history continuum in insular lizards: a comparison between species with invariant and variable clutch sizes

Abstract

Aim Both theory and empirical data suggest that life histories of insular species slow down (the “island syndrome”). Insular individuals are hypothesized to lay smaller clutches of larger eggs compared with individuals belonging to closely related mainland species. Most lizards have variable clutch sizes and can lay any number between one egg and a species‐specific maximum which can be well over 50 eggs. Many lizards, such as geckos and anoles, however, lay invariant small clutches of one or two eggs, and may thus be unable to manifest some aspects of the island syndrome. We tested whether insular species with either variable or invariant clutch sizes respond to insularity differently. Location Worldwide. Methods We assembled data on egg, clutch, hatchling and female sizes and brood frequencies of 2,511 lizard species. We tested whether the predictions of the island syndrome were met for lizards laying invariant versus variable clutches, controlling for female size and phylogenetic non‐independence. We further examined whether geckos and anoles, the major clades with invariant clutches, differ from other lizards in the way they respond to insularity. Results On islands, species with variable clutch sizes lay smaller clutches of larger eggs, from which larger hatchlings emerge, compared with mainland species. Lizards with invariant clutch sizes, however, decrease clutch size and increase clutch frequency but not hatchling or egg size, compared with mainland species. Main conclusions Lizards with invariant clutch sizes may be unable to increase egg and hatchling sizes because of limitations set by the female body cavity and pelvic opening, or by arboreality. They nonetheless lay smaller clutches on islands and increase clutch frequency. We suggest that this may result from lower seasonality of tropical islands, leading to a greater spread of reproductive effort. Alternatively, the higher clutch frequency on tropical islands could result from fluctuations in population densities caused by tropical storms.

Traits of lizards of the world: Variation around a successful evolutionary design

“…As expected, insularity (Covas, 2012;Novosolov, Raia, & Meiri, 2013;Schwarz & Meiri, 2017;Siliceo & Diaz, 2010) has a negative effect on clutch size: and insular species lay clutches that are 78% the size of continental species (with female mass and family as covariates).…”

“…As expected, insularity (Covas, ; Novosolov, Raia, & Meiri, ; Schwarz & Meiri, ; Siliceo & Diaz, ) has a negative effect on clutch size: and insular species lay clutches that are 78% the size of continental species (with female mass and family as covariates). Age at sexual maturity (log transformed) is not significantly different on islands than on the mainland (log transformed, corrected for family and species’ mass; insular species have a 5.9% higher intercept: 0.025 ± 0.024, p = 0.28).…”

A biogeographic reversal in sexual size dimorphism along a continental temperature gradient

“…The niche divergence hypothesis posits that, when interspecific competitors are few, intraspecific competition between males and females generates disruptive selection between males and females, producing sexual size dimorphism in either direction (Schoener 1977, Slatkin 1984, Shine 1989, Dayan and Simberloff 2005, Pincheira-Donoso et al 2009, Meiri et al 2014. As larger females can produce larger clutches and/or hatchlings (Meiri et al 2012, Schwarz andMeiri 2017), strong fecundity selection could favour increases in female size, possibly leading to femalebiased SSD (Shine 1988, Pincheira-Donoso and Tregenza 2011, Pincheira-Donoso and Hunt 2017. Fecundity selection acts on females to maximize reproductive output, via larger clutches and/ or offspring, in contrast to sexual selection which acts on mating success and viability selection which acts on survival (Pincheira-Donoso and Hunt 2017).…”

Ecology of the growth of Anolis nebulosus (Squamata: Dactyloidae) in a seasonal tropical environment in the Chamela region, Jalisco, Mexico

“…Therefore, the species falls near the fast end of the fast–slow life‐history continuum (Schwarz & Meiri, ). All these characteristics are linked to abiotic and biotic factors, such as precipitation, temperature, and food (Ballinger & Congdon, ; Meiri et al, ; Schwarz & Meiri, ). However, our results showed that these environmental factors had little effect on the growth rate of males and females.…”

“…The total number of insects refers to the total number of prey items in all categories reproductive season. Therefore, the species falls near the fast end of the fast-slow life-history continuum (Schwarz & Meiri, 2017). All these characteristics are linked to abiotic and biotic factors, such as precipitation, temperature, and food (Ballinger & Congdon, 1980;Meiri et al, 2013;Schwarz & Meiri, 2017).…”