Natural history of the lizards of the three kings Islands, New Zealand

The island rule explains consistent patterns of body size evolution in terrestrial vertebrates

Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called 'island rule' provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island-mainland populations of terrestrial vertebrates. We show that 'island rule' effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.

Skeletal variation in extant species enables systematic identification of New Zealand's large, subfossil diplodactylids

New Zealand’s diplodactylid geckos exhibit high species-level diversity, largely independent of discernible osteological changes. Consequently, systematic affinities of isolated skeletal elements (fossils) are primarily determined by comparisons of size, particularly in the identification of Hoplodactylus duvaucelii, New Zealand’s largest extant gecko species. Here, three-dimensional geometric morphometrics of maxillae (a common fossilized element) was used to determine whether consistent shape and size differences exist between genera, and if cryptic extinctions have occurred in subfossil ‘Hoplodactylus cf. duvaucelii’. Sampling included 13 diplodactylid species from five genera, and 11 Holocene subfossil ‘H. cf. duvaucelii’ individuals. We found phylogenetic history was the most important predictor of maxilla morphology among extant diplodactylid genera. Size comparisons could only differentiate Hoplodactylus from other genera, with the remaining genera exhibiting variable degrees of overlap. Six subfossils were positively identified as H. duvaucelii, confirming their proposed Holocene distribution throughout New Zealand. Conversely, five subfossils showed no clear affinities with any modern diplodactylid genera, implying either increased morphological diversity in mainland ‘H. cf. duvaucelii’ or the presence of at least one extinct, large, broad-toed diplodactylid species.

Comparative phylogeography of three skink species (Oligosoma moco, O. smithi, O. suteri; Reptilia: Scincidae) in northeastern New Zealand

Sea-level fluctuations during the Pliocene and Pleistocene have shaped the landscape of the Northland region of New Zealand. We examined the comparative phylogeography of three skink species (Oligosoma moco, O. smithi, O. suteri) in northeastern New Zealand in order to investigate the impact of the historical processes that have prevailed since the Pliocene on the Northland fauna. O. moco, O. smithi and O. suteri have similar distributions across northeastern New Zealand, frequently occurring in sympatry. We obtained sequence data from across the entire range of each species, targeting the ND2 mitochondrial gene. Using Neighbor-Joining, Maximum likelihood and Bayesian methods, our analysis revealed contrasting phylogeographic patterns in each species. We found substantial phylogeographic structure within O. moco, with three distinct clades identified. Similarly, deep phylogeographic divergence was evident within O. smithi, with three distinct clades present. Clade 1 included O. smithi populations from the Three Kings Islands and the western coastline of Northland, while Clade 2 encompassed the remainder of the range. However, since Clade 3 corresponded to a described species (O. microlepis), O. smithi might represent a species complex. In both O. moco and O. smithi, divergences among clades are estimated to have occurred in the Pliocene, with divergences within clades occurring during the Pleistocene. In contrast, genetic divergence among O. suteri populations was extremely limited and indicative of more recent divergences during the Pleistocene. The lack of phylogeographic structure in O. suteri might be a consequence of its oviparous reproductive mode, which restricted its distribution to warm northern refugia during glacial maxima. Differences in the ecology and biology of each species might have produced contrasting responses to the same historical processes, and ultimately diverse phylogeographic patterns. Our study reveals an absence of consistent and concordant phylogeographic patterns in the Northland biota, even within the same taxonomic group.