TY - JOUR

T1 - Response of saproxylic beetles to small-scale habitat connectivity depends on trophic levels

AU - Buse, Jörn

AU - Entling, Martin H.

AU - Ranius, Thomas

AU - Assmann, Thorsten

PY - 2016/6/1

Y1 - 2016/6/1

N2 - Context: According to the trophic-rank hypothesis, species may be differentially affected by habitat isolation due to their trophic position in the food chain, i.e. high-order trophic levels may be more negatively affected than low-order levels. Objectives: The aim of this paper is to study how species richness, abundance and composition of saproxylic beetle communities are affected by patch (=tree) quality and small-scale patch connectivity. Following the trophic-rank hypothesis, we expected predators to be more negatively affected by patch isolation than wood-feeding beetles. Methods: We studied the beetle community, patch connectivity and patch quality on 28 large oaks. Different connectivity measures were calculated using 50 m-buffers around trees and using distances to the five nearest trees. Results: Beetle species richness increased with the diameter of oaks, i.e. patch quality. No evidence of the trophic-rank hypothesis was found for species richness patterns. In accordance with the trophic-rank hypothesis, abundance of predatory beetles increased with patch connectivity but lower trophic levels were unaffected or even decreased with patch connectivity. Conclusions: The structure of invertebrate communities on trees changes with small-scale patch connectivity due to a differential response of low-order and high-order trophic levels. Isolated trees are more exposed to the sun than the more connected trees, which may affect the beetles; however, it was impossible to distinguish the microclimatic from the spatial effects. Although scattered trees generally have a higher conservation value than trees in forests, we conclude that forest trees may be more important for certain trophic levels.

AB - Context: According to the trophic-rank hypothesis, species may be differentially affected by habitat isolation due to their trophic position in the food chain, i.e. high-order trophic levels may be more negatively affected than low-order levels. Objectives: The aim of this paper is to study how species richness, abundance and composition of saproxylic beetle communities are affected by patch (=tree) quality and small-scale patch connectivity. Following the trophic-rank hypothesis, we expected predators to be more negatively affected by patch isolation than wood-feeding beetles. Methods: We studied the beetle community, patch connectivity and patch quality on 28 large oaks. Different connectivity measures were calculated using 50 m-buffers around trees and using distances to the five nearest trees. Results: Beetle species richness increased with the diameter of oaks, i.e. patch quality. No evidence of the trophic-rank hypothesis was found for species richness patterns. In accordance with the trophic-rank hypothesis, abundance of predatory beetles increased with patch connectivity but lower trophic levels were unaffected or even decreased with patch connectivity. Conclusions: The structure of invertebrate communities on trees changes with small-scale patch connectivity due to a differential response of low-order and high-order trophic levels. Isolated trees are more exposed to the sun than the more connected trees, which may affect the beetles; however, it was impossible to distinguish the microclimatic from the spatial effects. Although scattered trees generally have a higher conservation value than trees in forests, we conclude that forest trees may be more important for certain trophic levels.

KW - Forest management

KW - Forest structure

KW - Scattered trees

KW - Trophic-rank hypothesis

KW - Wood-inhabiting beetles

KW - Sustainability Science

KW - Geography

KW - Environmental planning

UR - http://www.scopus.com/inward/record.url?scp=84947705035&partnerID=8YFLogxK

U2 - 10.1007/s10980-015-0309-y

DO - 10.1007/s10980-015-0309-y

M3 - Journal articles

AN - SCOPUS:84947705035

VL - 31

SP - 939

EP - 949

JO - Landscape Ecology

JF - Landscape Ecology

SN - 0921-2973

IS - 5

ER -