The Middle to Late Pleistocene herpetofaunal assemblages from the Jarama and Manzanares valleys (Madrid, central Spain): an ecological synthesis

Abstract

The successive fossil amphibian and reptile assemblages from the Middle to Late Pleistocene sites from the Manzanares and Jarama River Valleys (Madrid, central Spain) permitted the reconstruction of part of the climate instability with high-amplitude and rapid shifts of the last 450 ka and their associated landscapes: Áridos-1 (MIS11b), Valdocarros II (MIS8a/7e), Estanque de Tormentas de Butarque ETB-H02 (MIS7d or MIS6), PRERESA (MIS7/6 or MIS5a) and HAT (MIS5a). This work aims to present a regional synthesis of the palaeoclimatic and palaeoenvironmental data obtained from the herpetofaunal assemblages for these two valleys and their influence on the biodiversity during the Pleistocene. As a whole, these archaeo-paleontological localities document a total of 20 taxa (8 anurans and 12 reptiles) thus representing 76.9% of the modern authochtonous herpetofauna of the southeast of the Region of Madrid. Taking as a reference the modern situation in the area, the successive herpetofaunal assemblages permits a hypothetical landscape reconstruction where three different periods are represented with a glacial landscape (ETB-H02), a landscape of transition from cool to temperate climatic conditions (Valdocarros II), and an interglacial landscape (Áridos-1, HAT, PRERESA, and today). Environment is particularly open during dry periods, independently of if it is cold or warm. The main difference between an interglacial and a glacial period is the opposite representation of woodlands vs. moist environments: the last ones being more represented during cold periods than during warm periods. Finally, as documented by the succession from Valdocarros II, periods of transition between cold and warm climate are more forested but at the expense of humid meadows progressively. According to the relation between richness, biodiversity and climatic and environmental factors, a clear correlation appears between reptile richness and woodlands. In a similar way, mean annual precipitation (MAP) is revealed to be the most influent factor on reptile local diversity certainly because of its implications on vegetal cover extension and ecosystem productivity and resources. For amphibians the MAP does not influence dominancy but species richness: anuran richness being higher for lower MAP. Such an unusual pattern is certainly due to the fact that there are no strict forest-dweller anurans within the archaeological assemblages and that most of the anurans present in the sites are well adapted to arid conditions.