The peninsula effect on species diversity: a reassessment of the avifauna of Baja California

Abstract

1999. The peninsula effect on species diversity: a reassessment of the avifauna of Baja California. -Ecography 22: 542-547.The peninsula effect, a decrease in species diversity from the base to the tip of peninsulas, has been proposed to explain the relatively poor species diversity of mammals on North American peninsulas. Subsequent work has questioned both the existence of peninsular declines in diversity, as well as the proposed cause (immigration-extinction dynamics). Previous studies of the Baja California avifauna have shown a gradual decrease in the diversity of breeding birds from the base to the tip of the peninsula. Using newly published data on the breeding land birds, I found a decrease only from the base to the middle of the peninsula, with a slight increase in diversity from the middle to the tip. This result is similar to that for other highly vagile taxa (e.g., Chiroptera, Lepidoptera) and is largely due to the concave diversity gradient of montane species along the peninsula. Habitat associations of the Baja avifauna and the location of potential source populations suggest that: 1) local habitat heterogeneity is likely the single most important factor influencing the avian diversity gradient along the peninsula; and 2) limited immigration of Neotropical species from mainland areas, and of Nearctic species from the base of the peninsula to the montane southern tip is partly responsible for the form of the diversity gradient along the southern half of the peninsula. My results, along with those from previous studies, suggest that rather than colonization/extinction dynamics, habitat heterogeneity and the vagility of the taxa considered have the greatest impact on the observed patterns of species diversity along peninsulas.

Efectos geográficos y ambientales sobre la distribución de las aves forestales ibéricas

“…Según este planteamiento, la pérdi-da de especies al aumentar la distancia a las áreas fuente (continente) sería una consecuencia de las dificultades crecientes que afrontan las poblaciones para paliar por inmigración los efectos de las extinciones locales en la dinámica colonizaciones-extinciones (Brown & Kodric-Brown, 1977;Brown & Lomolino, 1998). A pesar de que numerosos estudios han ilustrado este patrón, el efecto península no es un fenómeno universal que pueda observarse en cualquier región y/o sobre cualquier taxón o comunidad de organismos (Busack & Hedges, 1984;Brown, 1987;Wiggins, 1999). Es frecuente, por ejemplo, que las condiciones ambientales cambien al hacerlo la distancia al continente, enmascarando o distorsionando las predicciones del efecto península e, incluso, propiciando la aparición de patrones inversos (véase, por ejemplo, Brown & Opler, 1990 para un efecto península inverso en mariposas tropicales en Florida).…”

“…Se ha seña-lado, por ejemplo, la incidencia de factores ambientales (clima, heterogeneidad ambiental, etc. ;Milne & Forman, 1986;Schwartz, 1988;Wiggins, 1999), biológicos (capacidad dispersiva, amplitud de nicho, etc. ; Brown & Opler, 1990;Wiggins, 1999) e históricos (Busack & Hedges, 1984;Brown, 1987).…”

“…;Milne & Forman, 1986;Schwartz, 1988;Wiggins, 1999), biológicos (capacidad dispersiva, amplitud de nicho, etc. ; Brown & Opler, 1990;Wiggins, 1999) e históricos (Busack & Hedges, 1984;Brown, 1987). Por lo tanto, parece que la distribución de la riqueza de especies a lo largo de una península será el resultado final de una combinación de efectos ambientales y geográficos.…”

Combined effect of environmental factors on distribution of Geometridae (Lepidoptera) in South Korea

“…5), which could account for the peninsular effect on the geometrid moths in South Korea. The peninsular effect is reported for various groups of animals (birds, reptiles, butterflies, sphingid moths) and plants on different peninsulas, such as Baja California, Maine, Florida, Iberia, northern Thailand and Australia (Wiggins, 1999;Beck et al, 2007;Tubelis et al, 2007). On the Korean peninsula, butterflies (Choi, 2004) exhibit a similar peninsular effect to geometrid moths.…”

“…It is now widely accepted that the pattern of diversity on peninsulas may be a result of several factors, such as geographic orientation, ecological constraints, historical events and habitat diversity (Wiggins, 1999;Rahbek & Graves, 2001;Tubelis et al, 2007). On the Korean peninsula the combined effect of latitude and habitat diversity is recorded for butterfly species (Choi, 2004).…”