Iguana b&w text IGUANA • VOLUME 15, NUMBER 3 • SEPTEMBER 2008 179NATURAL HISTORY REPORTS Morphology and Diet of Two Sympatric Snakes PINTO ET AL. (2008. Amphibia-Reptilia 29:149–160) described the morphome- try and diet of two sympatric species of Chironius (C. flavolineatus and C. quadri- carinatus) from Brazilian Cerrado. The two species differ in external morphol- ogy, with C. flavolineatus longer and C. quadricarinatus heavier. Each species also showed marked sexual size dimorphism. Both species feed exclusively on frogs with a heavy preference for hylids, and may have a tendency to eat small prey. These two species have brownish ground colors and exhibit no ontogenetic varia- tion, suggesting that juveniles and adults use similar substrates. Chironius flavolin- eatus and C. quadricarinatus are semi- arboreal, forage actively, and usually feed on the ground. Chironius flavolineatus uses higher vegetation for resting and, based on morphological results, seems to be more arboreal than C. quadricarinatus. A unique life history among tetrapods: An annual chameleon living mostly as an egg The ~28,300 species of tetrapods (four- limbed vertebrates) almost exclusively have perennial life spans. KARSTEN ET AL. (2008. Proceedings of the National Academy of Sciences of the United States of America 105:8980–8984) discovered a remarkable annual tetrapod from the arid southwest of Madagascar: The chameleon Furcifer labordi, with a posthatching life span of just 4–5 months. At the start of the active season (November), an age cohort of hatchlings emerges; larger juve- niles or adults are not present. These hatchlings grow rapidly, reach sexual maturity in less than 2 months, and reproduce in January–February. After reproduction, senescence appears, and the active season concludes with popula- tion-wide adult death. Consequently, during the dry season, the entire popula- tion is represented by developing eggs that incubate for 8–9 months before syn- chronously hatching at the onset of the following rainy season. Remarkably, this chameleon spends more of its short annual life cycle inside the egg than out- side of it. A review of tetrapod longevity (>1,700 species) found no others with such a short life span. These findings sug- gest that the notorious rapid death of chameleons in captivity may, for some species, actually represent the natural adult life span. Consequently, a new appraisal may be warranted concerning the viability of chameleon breeding pro- grams, which could have special signifi- cance for species of conservation concern. World’s Smallest Snake Islands are viewed as natural evolutionary laboratories for terrestrial organisms because they have boundaries that limit dispersal and often reveal evolutionary patterns and mechanisms. One such pat- tern is that the smallest and largest species of different types of tetrapod ani- mals are frequently found on islands. HEDGES (2008. Zootaxa 1841: 1–30) described two new diminutive species of N A T U R A L H I S T O R Y R E P O R T S Both Chironius flavolineatus (top) and C. quadricarinatus (bottom) are semi-arboreal, forage actively, and usually feed on the ground, but the former is more slender and elongate, suggesting that it is more arboreal. LA U R IE J . V IT T Furcifer labordi from Madagascar spends most of its life inside an egg. C H R IS TO PH ER J . R A X W O R TH Y The Barbados Threadsnake (Leptotyphlops carlae) may be the world’s smallest species of snake. S. B LA IR H ED G ES Iguana 15.3 b&w text 9/10/08 5:44 AM Page 179 snakes of the genus Leptotyphlops from the Lesser Antilles: One from Saint Lucia (L. breuili) and the other from Barbados (L. carlae). The species from Barbados is the world’s smallest snake, with a total adult length of approximately 100 mm. Limited evidence indicates a clutch size of one and a greatly elongated egg shape. Comparison of egg shapes in snakes indi- cates that the shape is a packaging phe- nomenon, related primarily to the shape of the available body cavity and clutch size. The body shape of snakes also varies and influences the shape of snake eggs. The smallest snakes are typically stout- bodied, whereas the longest snakes usu- ally are more slender. The allometry of organ size also affects clutch size and shape, because the smallest snakes have the smallest proportion of body cavity space available for reproduction. The best explanation for the observation of body size extremes on islands is that colonizing species have adapted to open ecological niches that would otherwise be occupied on the mainland. Island colonists encounter novel environments and reduced interspecific competition, allow- ing species to evolve physical traits, including extremes in size, not normally seen on continents. However, the lower limit of adult size appears to be con- strained by the allometry of morphology, physiology, and reproduction. The small- est tetrapods have small clutches, usually one egg or young, and offspring that are relatively large. In the smallest snakes, offspring are one-half of the length of adults, compared with 10% adult length in the case of large species of snakes. Thus the evolutionary tradeoff between number and size of offspring appears to have reached a size boundary in these species, limiting the evolution of yet smaller species. Niche Relationships and Interspecific Interactions in Antiguan Lizard Communities Anolis lizards are the focus of most Caribbean lizard community ecology studies, with few studies including other common species that might influence community structure. To study niche relationships and interspecific interac- tions in Antiguan lizard communities, KOLBE ET AL. (2008. Copeia 2008: 261–272) used five offshore islands with varying combinations of three diurnal lizards: Ameiva griswoldi, Anolis leachii, and Anolis wattsi. The authors collected data on perch height, substrate, thermal microhabitat, body size, head length, daily activity, and abundance to charac- terize the ecological niche of each species. Ameiva griswoldi was more similar to A. leachii in size and daily activity, but more similar to A. wattsi in perch height, and A. leachii and A. wattsi were more similar in thermal microhabitat. This pattern of niche differentiation was consistent with niche complementarity, where species are similar on some niche axes but differ on others. Using the same niche characteris- tics as in species comparisons, we tested for a niche shift among islands for A. wattsi. In the absence of A. griswoldi, A. wattsi used lower perches, sunnier microhabitats, and was found more often on the ground. In contrast, with A. leachii absent, A. wattsi perched higher, more often in the shade, and on trunks. Furthermore, A. wattsi was most abun- dant when with A. leachii only, but least abundant when alone with A. griswoldi. These results suggest interspecific inter- actions, most likely due to competition and intraguild predation, are important for structuring Antiguan lizard commu- nities. 180 IGUANA • VOLUME 15, NUMBER 3 • SEPTEMBER 2008 NATURAL HISTORY REPORTS The Antiguan Ground Lizard, Ameiva gris- woldi, affected habitat use and abundance of Anolis wattsi on small islands near Antigua. JE N N IF ER D A LT R Y The Barbuda Bank Tree Anole (Anolis leachii) also affected habitat use by smaller Anolis wattsi on Antiguan satellite islands. C A R LO S A . R O D R ÍG U EZ G Ó M EZ Iguana 15.3 b&w text 9/10/08 5:44 AM Page 180