In defence of small habitat islands: Termites (Isoptera) in the Western Australian central wheatbelt, and the importance of dispersal power in species occurrence

Ecological theory has long undervalued the contribution of small remnants of native vegetation to nature conservation. This study provides data on colony persistence of remnant-dependent wood-eating termites in 28 remnants of mature wandoo (Eucalyptus capillosa) trees in paddock situations in the agricultural south-west of Western Australia. Remnants ranged in size from 2 to 30 trees, and in spatial isolation from 50 to 650 m. All remnants have been exposed to livestockrelated disturbance for >40 years. This study found that (1) Small remnants of eucalypt trees on farms retain important functional representatives, i.e., wood-eating termites for nutrient-cycling, and high species numbers. (2) Seventeen species have the capacity to establish and maintain colonies in remnants =5 trees. (3) Spatial isolation has no significant influence on the total number of termite species. (4) The number of trees (r = 0.60) and quantity of dead wood in the remnant (r = 0.86) were significant indicators of total termite species number. Larger remnants with low quantities of wood supported few termites, however. (5) Rare as well as common species persisted in small remnants. (6) Alate wing-size was a significant indicator of the occurrence of the six most common termite species in remnants (r = 0.84). The implication of isolation effects for rare species with limited powers of dispersal is self-evident, as is the need for the creation of habitat linkeages to reduce the effects of spatial isolation on the native fauna.