This paper documents interspecific and intraspecific differences in certain niche parameters among 3 species of lizards of the genus Anolis occurring in the southern Lesser Antilles. The 2 species whose ranges broadly overlap in Grenada show significant differences in body temperatures and food size distributions. Although there is considerable difference in the maximum size attained by the 2 species, animals with identical head and body lengths have radically contrasting distributions of prey size: smaller individuals of the larger species take larger food than larger individuals of the smaller species. The rate of increase of average prey length with increasing head length for the smaller species is lower than that for the larger one. In all species, the larger adult makes take significantly larger prey than adult females or subadult males. For the 2 species on Grenada, adult females take significantly smaller food than subadult males of the same species and head length; there is a slight reversal of this trend for the solitary species on Martinique. For all 3 species, adult males eat a greater amount of plant matter and draw more of their prey from fewer taxonomic categories than do lizards of the smaller—sized classes, In general, as the size of lizard increases, range of prey size increases and the number of prey items ingested decreases; variances for these distributions are quite large. Modes of niche segregation on Grenada are contrasted with those among anoles of other small islands, and hypotheses are offered as to how climatic features and the spatial arrangement of individuals of varying size within a species might determine the critical niche dimensions.

Many of the recent, widespread declines and disappearances of amphibian populations have taken place in seemingly undisturbed, montane habitats. The question of whether the observed patterns differ from those expected from natural population dynamics is the subject of an ongoing controversy with important implications for conservation. We examined this issue for the Monteverde region of Costa Rica’s Cordillera de Tilarán, where a multi‐species population crash in 1987 led to the disappearance of the endemic golden toad (  Bufo periglenes) and many other species. Focusing on long‐term studies of other amphibian assemblages, we developed probabilistic null models for the number of disappearances. Tests of these models at Monteverde suggest that the patterns observed there are highly improbable in the context of normal demographic variability. Twenty species of frogs and toads (40% of the anuran fauna) were missing throughout our 1990–1994 surveys of a 30‐km2 area. Not all organisms in this area had declined accordingly: the relative frequency of absences was much greater for anurans than for breeding birds. Nevertheless, anuran habitats, most of which are protected within the Monteverde Cloud Forest Preserve, seemed unchanged, and none of the breeding‐bird species known to be sensitive to deforestation was missing. Thus, only factors other than direct, obvious human impacts can explain the amphibian declines. Consistent with our tests of null models, analyses of recent population trends do not support the hypothesis that the 1987 crash was an extreme fluctuation from which populations are recovering. Surviving species for which baseline data are available—stream‐breeding glass frogs (  Hyalinobatrachium fleischmanni and Centrolenella prosoblepon) and a pond‐breeding treefrog (  Hyla pseudopuma)—remained far less abundant than they were before the crash and showed no increase during 1990‐1994. We documented an increase only for one terrestrial‐breeding rain frog ( Eleutherodactylus diastema).Pruebas de Modelos Nulos para Disminuciones de Anfibios en una Montaña TropicalMuchas de las disminuciones y desapariciones recientes de poblaciones de anfibios en varias partes del mundo se han producido en hábitats que aparentemente no han sido alterados. La pregunta de si los patrones observados difieren de lo que es predicho por la dinámica natural de poblaciones es el tema de una controversia actual que tiene consecuencias importantes para la conservación. Se examinó esta pregunta para la región de Monteverde en la Cordillera de Tilarán, Costa Rica, donde un colapso de poblaciones en 1987 produjo la desaparición del endémico sapo dorado (  Bufo periglenes) y muchas otras especies. Centrándose en estudios a largo plazo sobre anfibios de otras regiones, se desarrollaron modelos nulos probabilísticos con respecto al número de desapariciones. Al probarse estos modelos para Monteverde se sugiere que los patrones observados son poco probables dentro de los parámetros normales de la variabilidad demográfica. Durante 1990‐1994 en un área de 30‐km2, veinte especies de ranas y sapos (el 40% de los anuros de la región) estuvieron ausentes. No todos los organismos del área disminuyeron de la misma forma: por ejemplo, la frecuencia relativa de especies ausentes fue mucho mayor para los anuros que para las aves que se reproducen en el área de estudio. Sin embargo, la mayoría de los hábitats de anuros están protegidos dentro de la Reserva Biológica Bosque Nuboso de Monteverde, y no parecía que habían cambiado. Además, ninguna de las especies de aves que son afectadas de manera negativa por la deforestación estuvo ausente. Por lo tanto, las disminuciones de anfibios sólo pueden ser explicadas por factores que no son los impactos obvios y directos causados por los seres humanos. De acuerdo con nuestras pruebas de modelos nulos, los análisis de tendencias recientes de abundancia no apoyan la hipótesis de que el colapso de 1987 fuera una fluctuación extrema de la cual las poblaciones están recuperándose. Las especies sobrevivientes de las que existen datos demográficos anteriores al colapso—ranas de vidrio ( Hyalinobatrachium fleischmanni y Centrolenella prosoblepon), que se reproducen en quebradas, y una rana arborícola ( Hyla pseudopuma) que pone huevos en lagunas y pozos—eran mucho menos abundantes durante 1990–1994 de lo que fueron antes de este evento y no se encontró evidencias de aumento. Se documentó un incremento solo en las poblaciones de Eleutherodactylus diastema, que se reproduce en hábitats terrestres.

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Society of Ichthyologists and Herpetologists (ASIH)is collaborating with JSTOR to digitize, preserve and extend access to Copeia.Chromosomes of 17 species of teiid lizards, currently assigned to 11 genera were studied. Karotypes divided the Teiidae into three major groups. Dracaena, Callopistes, Crocodilurus, and Tupinambis have 2n = 34-38 chromosomes including five or six pairs of large metacentric macrochromosomes and a series of much smaller microchromosomes. Ameiva and its relatives (Cnemidophorus, Teius, Dicrodon, and Kentropyx) have 2n = 46-56 chromosomes, general absence of a distinct break between macroand microchromosomes, and a majority of large chromosomes acrocentric. Within the Ameiva group only Dicrodon and Teius have 2n above 52. Two "microteiids," Anadia bitaeniata and Pholidobolus montium have 2n = 46 chromosomes with a marked break between 10 pairs of macrochromosomes and 13 pairs of microchromosomes; many of the macrochromosomes are two-armed.Evolutionary pathways among these three groups are discussed. The general karyotype found in Dracaena and its relatives is found in many other lizard families, and often in the most primitive representatives of those families. This karyotype is considered primitive for the Teiidae. The karyotypes of Ameiva and its relatives are presumed to have evolved through centric fissions of the metacentric macrochromosomes from this primitive state. The microteiid karyotype is most similar to that of the Ameiva group and may have arisen through pericentric inversions in some of the acrocentric macrochromosomes of the ancestral stock.There is a distinct gap between the karotypes of all teiids studied to date and the karyotypes of the presumably closely related lacertids.

No abstract