Intraspecific competition and high food availability are associated with insular gigantism in a lizard

Pafilis, Panayiotis; Meiri, Shai; Foufopoulos, Johannes; Valakos, Efstratios D.

doi:10.1007/s00114-009-0564-3

Cited by 113 publications

(162 citation statements)

References 45 publications

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“…Rapid growth would be advantageous to achieve large size as quickly as possible and in some snails a more rapid growth rate also results in larger adult shell size (Goodfriend 1986). In a perhaps analogous situation, populations of lizards (Podarcis gaigeae) on certain small islands of the Aegean evolved giant forms that were thought to be the product of increased resource availability, leading to increased population densities and intraspecific competition (Pafilis et al 2009), which involved increased cannibalism so that the proximate cause of rapid growth to a larger size was increased predation (Pafilis et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda

Olson

Hearty

2010

Biol. Lett.

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During the last half million years, pulses of gigantism in the anagenetic lineage of land snails of the subgenus Poecilozonites on Bermuda were correlated with glacial periods when lower sea level resulted in an island nearly an order of magnitude larger than at present. During those periods, the island was colonized by large vertebrate predators that created selection pressure for large size and rapid growth in the snails. Extreme reduction in land area from rising seas, along with changes in ecological conditions at the onset of interglacial episodes, marked extinction events for large predators, after which snails reverted to much smaller size. The giant snails were identical in morphology during the last two glacials when the predators included a large flightless rail Rallus recessus (marine isotope stages (MIS) 4-2) and a crane Grus latipes and a duck Anas pachysceles (MIS 6). In a preceding glacial period (MIS 10), when the fauna also included the tortoise Hesperotestudo bermudae, the snails were not only large, but the shells were much thicker, presumably to prevent crushing by tortoises. Evolution of Poecilozonites provides an outstanding example of dramatic morphological change in response to environmental pressures in the absence of cladogenesis.

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Section: Discussionmentioning

confidence: 99%

Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda

Olson

Hearty

2010

Biol. Lett.

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“…In certain cases, a positive correlation has been demonstrated between the abundant presence of seabirds and body sizes in island lizards (Sanchez-Piñero & Polis 2000;Pafilis et al 2009). …”

Section: Size Differences and Ecological Considerationsmentioning

confidence: 99%

Morphometric and genetic divergence in island and mainland populations ofAnolis nebulosus(Squamata: Polychrotidae) from Jalisco (Mexico): an instance of insular gigantism

Senczuk

García

Colangelo

et al. 2014

Italian Journal of Zoology

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The clouded anole Anolis nebulosus (Squamata: Polychrotidae) is widespread on the Pacific coast of Mexico. The species also inhabits Don Panchito, a small islet located near the coast of the Chamela-Cuixmala Biosphere Reserve in the state of Jalisco. We studied the extent of intraspecific differences in morphology (absolute size and body proportions) and in mtDNA sequences (16S and NDH2) between the population living on the islet (N = 18 for morphometry; N = 12 for mtDNA) and the one on the facing mainland (N = 38 for morphometry; N = 16 for mtDNA). The individuals on the islet are larger than those on the mainland with little overlap in size for either males (islet: 52.79 ± 1.82 mm; mainland: 40.96 ± 2.99 mm) or females (islet: 46.18 ± 3.24 mm; mainland 37.14 ± 2.13 mm). The presence of insular gigantism, as here found in A. nebulosus, seems uncommon in the genus and could be explained as a combination of low predation pressure and higher intraspecific competition on the island. Moreover, we found that sexual dimorphism (SD) is higher in the island population than in the mainland one. The molecular analysis shows the absence of shared haplotypes between the island and mainland populations. Ten mtDNA haplotypes belonged to the mainland population and three to the island population. The shape of the minimum spanning network and of the mismatch distribution indicates a single colonization event. These molecular data indicate a certain degree of isolation of the island population notwithstanding its proximity to the coast. The morphological characteristics of the anoles on Don Panchito match with the expectation of the so-called "reversed island syndrome" theory, which predicts an increased body size and sexual dimorphism in lizards living on very small islands characterized by unpredictable environmental conditions.

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“…Organisms can reduce their overall energy demand in two fundamental ways. First, they can reduce their body size by reducing energy allocation to growth, which simultaneously reduces total energy expenditure for maintenance (Blanckenhorn 2000;Wikelski and Romero 2003;Pafilis et al 2009;McNab 2010). Second, organisms can reduce metabolic rate independently of body size, which changes the allometric relationship between metabolism and body size (Guppy and Withers 1999;Wang et al 2006;Burton et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Reduction of Energetic Demands through Modification of Body Size and Routine Metabolic Rates in Extremophile Fish

Passow¹,

Greenway²,

Arias‐Rodríguez³

et al. 2015

Physiological and Biochemical Zoology

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Variation in energy availability or maintenance costs in extreme environments can exert selection for efficient energy use, and reductions in organismal energy demand can be achieved in two ways: reducing body mass or metabolic suppression. Whether long-term exposure to extreme environmental conditions drives adaptive shifts in body mass or metabolic rates remains an open question. We studied body size variation and variation in routine metabolic rates in locally adapted populations of extremophile fish (Poecilia mexicana) living in toxic, hydrogen sulfide-rich springs and caves. We quantified size distributions and routine metabolic rates in wild-caught individuals from four habitat types. Compared with ancestral populations in nonsulfidic surface habitats, extremophile populations were characterized by significant reductions in body size. Despite elevated metabolic rates in cave fish, the body size reduction precipitated in significantly reduced energy demands in all extremophile populations. Laboratory experiments on common garden-raised fish indicated that elevated routine metabolic rates in cave fish likely have a genetic basis. The results of this study indicate that adaptation to extreme environments directly impacts energy metabolism, with fish living in cave and sulfide spring environments expending less energy overall during routine metabolism.

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Intraspecific competition and high food availability are associated with insular gigantism in a lizard

Cited by 113 publications

References 45 publications

Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda

Predation as the primary selective force in recurrent evolution of gigantism in Poecilozonites land snails in Quaternary Bermuda

Morphometric and genetic divergence in island and mainland populations ofAnolis nebulosus(Squamata: Polychrotidae) from Jalisco (Mexico): an instance of insular gigantism

Reduction of Energetic Demands through Modification of Body Size and Routine Metabolic Rates in Extremophile Fish

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