Geographic consistency in the seed dispersal patterns of Taxus baccata L. in the Iberian Peninsula

Abstract

Aim of the study: Seed dispersal is a crucial process in tree population dynamics. In the case of yew, Taxus baccata L., seeds are dispersed by birds and mammals in a non-random, microhabitat-dependent way, a pattern constraining population renewal and expansion. While skewed dispersal has been frequently found, we lack knowledge on how consistent are spatial restrictions across time and yew’s geographical range. This sort of information is required for the development of trans-regional management tools for this species.

Area of study: Three Taxus baccata stands across Spain, namely Cantabrian Range, Sierra de Gredos and Sierra de Cazorla.

Material and methods: During two consecutive years, we have been studying the contribution of frugivorous animals to the seed dispersal patterns of Taxus baccata L., in three ecologically contrasted localities of the Iberian Peninsula.

Main results: The spatial distribution of the seeds in the landscape was very heterogeneous, with the majority of the seeds consistently dispersed into forested microhabitats and almost none outside the forest. The main seed dispersers were always frugivorous birds, particularly thrushes (Turdus merula, T. viscivorus, T. philomelos and T. iliacus).

Research highlights: The results highlighted the large-scale consistency of the seed dispersal system of Taxus baccata. We suggest that the generalized spatially-restricted dispersal contributes to the lack of regeneration and absence of population expansion of the species all over its range. As a trans-regional conservation strategy, we recommend measures aimed at maintaining as much as diverse assemblage of frugivores in order to provide complementary seed dispersal and therefore enhance population regeneration and expansion.

Keywords: English Yew; frugivory; seed rain; microhabitats; Turdus spp.; carnivorous mammals; spatially-restricted dispersal.