Female reproductive cycles in the northernmost populations of the two gekkonid lizards, Hemidactylus frenatus and Lepidodactylus lugubris

One or two eggs: what underlies clutch size variation within a gecko species?

Although the majority of reptiles show variable clutch sizes, geckos have a fixed clutch size (one or two eggs) and modify reproductive output by changing the offspring size or clutch frequency. However, the clutch size of several geckos is not strictly fixed at the species level; they actually lay both single- and double-egg clutches. We still do not fully understand if clutch size variation within a gecko species is due to adaptive control or reproductive failure like accidental absorption of one of two eggs. This study investigated differences between single- and double-egg clutches of a gecko species in terms of reproductive frequency, egg size, and offspring trait. I housed mourning geckos Lepidodactylus lugubris in a controlled environment and observed their reproduction for seven years. No large differences between single- and double-egg clutches were detected in reproductive frequency and egg size, indicating that life-history trade-offs do not explain much about clutch size variation. Single-egg was comparable in egg size to double-egg, but hatchlings from single-egg showed significantly lower body condition than did those from double-egg. These results suggest that the single-egg is not only a reduction of reproductive output per clutch, but it may provide negative effect on ontogeny.

Continuous expansion of the geographic range linked to realized niche expansion in the invasive Mourning gecko Lepidodactylus lugubris (Duméril & Bibron, 1836)

Lepidodactylus lugubris is a parthenogenetic gecko which has been increasingly expanding its range during the last century. This invasive species has been reported from multiple tropical and subtropical countries in five continents, most of which were colonized in recent times. In order to understand how the realized niche of the species was affected by this dramatic geographic range expansion, we reconstructed the history of the geographic range expansion. We built models of the realized niche of the species at different points in time during the invasion process. This was achieved through the implementation of modern hypervolume construction methods, based on the Hutchinson's niche concept. The models were then compared to detect possible realized climatic niche expansion over time. Furthermore, we investigated possible pathways used by the species to spread. A progressive expansion of the realized niche was identified. As the species spread into new areas, we observed a tendency to colonize regions with warmer temperatures and higher precipitation rates. Finally, we found evidence for cargo shipping being the major pathway through which the species expands its range. Further studies on this topic should aim to investigate the role of biological interactions, and how they shape the distribution of L. lugubris on a global scale. A deeper understanding of this kind of processes will help us tackle the issue of invasive species, which has become a major challenge in conservation biology.

Predatory functional responses under increasing temperatures of two life stages of an invasive gecko

The direct effects of temperature increases and differences among life-history might affect the impacts of native and invasive predators on recipient communities. Comparisons of functional responses can improve our understanding of underlying processes involved in altering species interaction strengths and may predict the effect of species invading new communities. Therefore, we investigated the functional responses of the mourning gecko Lepidodactylus lugubris (Duméril & Bibron, 1836) to explore how temperature, body-size and prey density alter gecko predatory impacts in ecosystems. We quantified the functional responses of juvenile and adult geckos in single-predator experiments at 20, 23 and 26 °C. Both displayed saturating Type-II functional responses, but juvenile functional responses and the novel Functional Response Ratio were positively affected by temperature as juvenile attack rates (a) increased as a function of increased temperature. Handling times (h) tended to shorten at higher temperature for both predator stages. We demonstrate that the effects of temperature on functional responses of geckos differ across ontogeny, perhaps reflecting life-history stages prioritising growth and maturation or body maintenance. This indicates that temperature-dependent gecko predatory impacts will be mediated by population demographics. We advocate further comparisons of functional responses to understand the invasiveness and future predatory impacts of geckos, and other invasive species globally, as temperatures change.

Comparison of personality between juveniles and adults in clonal gecko species

The developmental perspectives of animal personality enhance our understanding of how personality structure changes in relation to life stage. Clonal animals are ideal models for developmental studies because personality differences can be solely attributed to environmental factors. Here, I investigated the presence of personality within a species of clonal gecko, Lepidodactylus lugubris, at different developmental stages. For juveniles and adult geckos, I measured exploration (reaction to a novel situation) and boldness (risk-prone tendency) and evaluated repeatability and correlation of these behavioural traits. Each gecko exhibited different exploration and boldness with significant repeatability through time but no correlation between these behavioural traits. Small juveniles were composed of only bold and low explorative individuals but large juveniles and adults were composed of various personality type individuals. These results demonstrate that subject geckos have a similar personality structure across life stages and that exploration and boldness are independent personality without forming behavioural syndrome structure. Biased composition of personality type between life stages suggests that appearance of different personality type individuals during an early ontogenetic stage generates personality variation within the clonal population. This study provides developmental insight about personality structure and its composition in clonal animals living in the wild.

Maternal basking regime has complex implications for birthdate and offspring phenotype in a nocturnally foraging, viviparous gecko

Maternal basking regime can affect gestation length in viviparous squamates, but effects on offspring phenotype in species with extended pregnancies and ability to delay the birth season are unclear. We investigated the effects of three maternal basking regimes on maternal thermoregulation, gestation length, pregnancy outcome and offspring phenotype in the gecko Woodworthia “Otago/Southland”. This long-lived (30+ years), nocturnal forager has field pregnancies lasting up to 14 mo, with fully developed offspring maintained in utero over winter. Within regimes, we also compared outcomes for spontaneous (early) deliveries with those from induced (late) deliveries to test the ‘adaptive prolongation of pregnancy’ hypothesis. Although a cool regime significantly extended gestation, the effect was reduced by increased maternal basking, and embryonic development under the cool regime was just as successful. Offspring from spontaneous births (but not induced births) were smaller and grew more slowly when from the cool regime. However, induced offspring did not differ in consistent ways from those delivered spontaneously and offspring from all groups had high viability, similar use of warm retreat sites and similar sprint speeds. Thus, consistent evidence for ‘adaptive prolongation of pregnancy’ was lacking. Unusually for squamates, pregnant females can begin vitellogenesis before giving birth, and a profound drop in maternal body temperature near the end of pregnancy (∼6.3°C, confirmed under the warm regime) may assist survival of embryos in utero. Female lizards that maintain fully-developed embryos in utero have the potential to make complex trade-offs among birthdate, offspring phenotype and future reproduction.

Comparison of a native and a non-native insular reptile species

This study compared the life histories of Hemidactylus frenatus, a significant invasive gecko, and Phyllodactylus palmeus, a Honduran endemic, over 10 wk, June–August 2013 at 12 study sites on the Honduran island of Cayo Menor of the Cayo Cochinos archipelago where H. frenatus arrived in 2008. Three different life-history traits related to invasion success were measured: body size, fecundity and population size. During the study 140 natives and 37 non-natives were captured, weighed, measured and marked uniquely. The number of gravid females and number of eggs were also recorded. Phyllodactylus palmeus was the significantly larger of the two species (60% larger mass, 25% longer SVL) and had higher population abundance at all 12 study sites with some sites yielding no H. frenatus individuals. However, H. frenatus had a larger proportion of gravid females. Observations that the native species is more common despite being sympatric with a known aggressive invader suggest two possibilities: the island is at the start of an invasion, or that the two species co-exist in a more stable fashion.

Comparative Chromosome Painting and NOR Distribution Suggest a Complex Hybrid Origin of Triploid Lepidodactylus lugubris (Gekkonidae)

Parthenogenesis, unisexuality and triploidy are interesting but poorly studied phenomena occurring in some reptile species. The mourning gecko (Lepidodactylus lugubris) represents a complex of diploid and triploid parthenogenetic mostly all-female populations (males occur quite rarely) widely distributed in coastal areas of the Indian and Pacific Oceans. Here, we study karyotypes of a male and two female L. lugubris (LLU) triploid individuals (3n = 66) using comparative painting with Gekko japonicus, Hemidactylus turcicus and H. platyurus chromosome specific probes to visualize the homologous regions and to reveal genus specific rearrangements. Also, we applied a 28S ribosomal DNA probe and Ag-staining to detect nucleolus organizer regions (NORs). Our results suggest that the karyotype of L. lugubris underwent a chromosome fission and a fusion after its divergence from a common ancestor of the Gekko-Hemidactylus group. The NORs were found to be located on one out of three homologs on each of LLU8, LLU15 and LLU18, thus further confirming a hybrid origin of triploid individuals. It seems that three different bisexual populations might have contributed to the origin of this triploid parthenogenetic population. We postulate that the heterozygosity in NOR localization is maintained in the triploid clone studied by the absence of recombination as described in whiptail lizards. The pattern of NOR localizations and homologous regions in males and females, as well as the absence of other detectable karyotypic differences, suggest that males arise spontaneously in all female populations and do not arise from independent hybridizations with different species.

WHY DO MOST TROPICAL ANIMALS REPRODUCE SEASONALLY? TESTING HYPOTHESES ON AN AUSTRALIAN SNAKE

Most species reproduce seasonally, even in the tropics where activity occurs year-round. Squamate reptiles provide ideal model organisms to clarify the ultimate (adaptive) reasons for the restriction of reproduction to specific times of year. Females of almost all temperate-zone reptile species produce their eggs or offspring in the warmest time of the year, thereby synchronizing embryogenesis with high ambient temperatures. However, although tropical reptiles are freed from this thermal constraint, most do not reproduce year-round. Seasonal reproduction in tropical reptiles might be driven by biotic factors (e.g., peak periods of predation on eggs or hatchlings, or food for hatchlings) or abiotic factors (e.g., seasonal availability of suitably moist incubation conditions). Keelback snakes (Tropidonophis mairii, Colubridae) in tropical Australia reproduce from April to November, but with a major peak in May-June. Our field studies falsify hypotheses that invoke biotic factors as explanations for this pattern: the timing of nesting does not minimize predation on eggs, nor maximize food availability or survival rates for hatchlings. Instead, our data implicate abiotic factors: female keelbacks nest most intensely soon after the cessation of monsoonal rains when soils are moist enough to sustain optimal embryogenesis (wetter nests produce larger hatchlings, that are more likely to survive) but are unlikely to become waterlogged (which is lethal to eggs). Thus, abiotic factors may favor seasonal reproduction in tropical as well as temperate-zone animals.

Endoparasites of three species of house geckoes in Lampung, Indonesia

Thirty-four house geckoes (21 Cosymbotus platyurus, four Gehyra mutilata and nine Hemidactylus frenatus) in December, 1997 (rainy season) and 26 geckos (16 C. platyurus, six G. mutilata and four H. frenatus) in July, 2000 (dry season) were captured in Lampung, Indonesia. Some species of geckoes have been inadvertently introduced to many tropical regions from their native region, but the three species of geckoes in this study are native to Indonesia. Six species of endoparasites were recovered: Oochoristica javanensis (Cestoda) from the small intestine, Paradistomum geckonum (Digenea) from the small intestine and gallbladder, Postorchigenes ovatus (Digenea) from the small intestine, Spauligodon hemidactylus (Nematoda) from the large intestine, and Raillietiella gehyra and R. frenatus (Pentastomida) from the lungs. The prevalence and mean intensity of infection in each species of geckoes are also presented. The prevalence of S. hemidactylus from C. platyurus and H. frenatus in the rainy season was significantly higher than in the dry season. The low prevalence of S. hemidactylus in G. mutilata in the present study corresponded to a previous report from a non-native area. According to the original description, the male of S. hemidactylus lacked a spicule, but in the present study, one male was found with a spicule. The present study suggests male dimorphism occurs in Spauligodon. The number of endoparasite species and snout vent length of geckoes were positively correlated. Geckoes with high worm burdens may be more easily captured by predators.