‘Peninsula effect’ and Italian peninsula: matherials for a review and implications in applied biogeography

Abstract

Biogeographia vol. XX VII - 2006 (Pubblicato il 30 dicembre 2006) Biogeografia deIl’Appenn/no centrale e settentrionale: trenfanni dopo ‘Peninsula effect’ and Italian peninsula: matherials for a review and implications in applied biogeography CORRADO BATTISTI Uflicio Comerwzzione Nzztum, Serz/izio Ambimte, Provincial di Roma, Vizz Til9urtimz 69], 00159 Roma {Ital}/),' e—maz'[: c. bzzttisti @p rozzimizz. ramzz. it Key words: patterns, processes, alfa and gamma diversity, Apennine effect, conservation SUMMARY ‘Peninsula effect’ (a reduction of species number from base to tip along the peninsulas, more evident when comparing this parameter versus equally-sized mainland regions) appeared to be not a general pattern, but an occasional phenomenon shown in some species assemblages (communities, taxocoenosis, ecological guilds) in specific contexts. These patterns can be different if related to different taxa, scales, ecological/taxonomic levels and no single theory was widely accepted to explain their causal processes. In this paper, an overview on a wide literature evidences as the causal factors/processes that might explain peninsular diversity patterns should be reconducted to following groups: 1) recent stochastic factorsl processes (equilibrium and derived island biogeography theories); 2) historical events as paleoclimate oscillations, paleogeographic and tectonic changes (‘diversity disequilibrium models’); 3) recent (deterministic) factors/processes (ecology, climate, geography), with a base—tip gradient; 4) anthropical recent factors/ processes (habitat fragmentation and disturbances), with a base—tip gradient. A cautionary approach is requested when comparing, along a peninsular gradient, data from cells or bands at regional/ landscape scale (‘Y-diversity level) or from single ecosystems/fragments (0t—diversity level) because causal factors could be different in explain the observed patterns (respectively, heterogeneity at landscape scale and equilibrium dynamics). Causal processes for ‘inland/peninsulas’ are different in respect to ‘oceanic/geographic’ ones and could be studied with a landscape ecology approach: therefore, we can introduce a ‘peninsular biogeographic theory applied to inland peninsular—shaped ecosystems’ analogously to ‘island biogeography theory applied to mainland’. The Italian peninsula shows a wide latitudinal range, a collocation in a specific Mediterranean scenario, a peculiar orographic pattern represented from Apennines (role as longitudinal 'bridge’ and as trasversal ‘barrier’). These specific features, analogously to others present in some peninsulas (e.g., ‘Everglades’ in Florida, ‘Central desert’ in Baja California’), affect the diversity patterns in many taxa, assemblages and single species. Peninsular data could be utilized in multiscale conservation strategies (from landscape to regional level) and this issue could be related to applied biogeography, other than to the descriptive and causal biogeography. A INTRODUCTION The analysis of distribution patterns of the species and groups and their causal processes appears the main research focus in macroecology and biogeography (e.g., from W/allace, 1876). ‘Peninsula effect’ (Simpson, 1964) is a Widely studied issue.