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Post‐dispersal seed depletion by rodents in marginal populations of yew ( T axus baccata ): consequences at geographical and local scales
Author(s) -
Sanz Rubén,
Pulido Fernando
Publication year - 2014
Publication title -
plant species biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 36
eISSN - 1442-1984
pISSN - 0913-557X
DOI - 10.1111/1442-1984.12030
Subject(s) - biology , predation , seed predation , biological dispersal , seed dispersal , ecology , population , threatened species , habitat , frugivore , herbivore , seed dispersal syndrome , rodent , demography , sociology
Post‐dispersal seed predation is a crucial phenomenon for plant recruitment, and its incidence can be hypothesized to increase in ecologically and geographically marginal populations of threatened species, such as yew ( T axus baccata ). Here we examine the among‐ and within‐population patterns of seed consumption by rodents and evaluate to what extent they are linked to marginality in M editerranean low‐density yew stands. Among populations we tested: (i) whether the rates of seed predation found in our marginal sites were consistently higher than in populations from core regions; (ii) within populations we evaluated whether rodents preferred microhabitats with greater seed availability (beneath female yew trees) or with lower predation risk (shrubs) in two seeding seasons (fall–winter 2005 and 2006). Predation rates were extremely high (92.5%) and they were well above values reported for core populations (65.4%), to the extent that rodents almost completely depleted the experimental seeds in all populations and years. Our expectation of lower predation rates with decreasing vegetation cover was also confirmed for all years and populations, suggesting that rodent foraging was risk‐sensitive. This microhabitat effect outweighed the effect of seed availability under female yew trees, implying also that rodents selectively consumed the most valuable seeds in terms of their recruitment prospects. Overall, our results suggest that the mechanisms underlying seed depletion and its demographic consequences are linked to the effects of reduced yew performance in ecologically marginal habitats.