Conservation

Cockroaches are not generally considered a charismatic taxon; species that are threatened with extinction are unlikely to rally conservationists to action. They are nonetheless an integral part of a stable and productive ecosystem in tropical rainforest and other habitats. Cockroaches deserve our consideration and respect for the range of services they perform and for their membership in an intricate web of interdependent and interacting flora, fauna, and microbes. Many cockroach species live in habitats of conservation concern and are threatened by canopy removal, urbanization, and agricultural practices. Philopatric species with naturally small population sizes and specific habitat requirements are particularly vulnerable to perturbations (Pimm et al., 1995; Tscharntke et al., 2002; Boyer and Rivault, 2003). These taxa are frequently wingless, and their consequent low dispersal ability makes them vulnerable to habitat fragmentation and genetic bottlenecks. Several species of Australian burrowing cockroaches have restricted ranges and are affected by farming/forestry practices or by urbanization. The accompanying soil disturbance, soil compaction, and loss of their leaf litter food sources have devastated some populations of these unique insects (H.A. Rose, pers. comm. to CAN).

Caves are delicately balanced and vulnerable ecosystems whose resident cockroaches can be severely affected by guano compaction, guano collection, and other human disturbances (Braack, 1989). Nocticola uenoi miya-koensis, for example, became rare in the largest known limestone cave on Miyako-jima Island after it was opened to tourists (Asahina, 1974), and the invertebrate community of an Australian cave disappeared due to soil compaction by human visitors (Slaney and Weinstein, 1997a). According to Gordon (1996), the cave-dwelling species Aspiduchus cavernicola (Tuna Cave cockroach) living in a network of caves in southern Puerto Rico is officially classified as a "species at risk"by the U.S. Fish and Wildlife Service. Roth and Naskrecki (2003) recently described a new species of cave cockroach collected during a Conservation International survey of West African sites under threat from large-scale mining operations. The removal of cave cockroaches for scientific study also can have a significant impact on their populations (Slaney and Weinstein, 1997a).

Global warming and the resultant decrease in snow cover at high elevations may put cockroaches such as the

New Zealand alpine species Celatoblatta quinquemacu-lata at risk (Sinclair, 2001). Although the species is physiologically protected against the cold, it relies on the thermal buffering effect of snow cover in particularly harsh winters. Reduced snow cover results in an increased number of freeze-thaw cycles and lower absolute minimum temperatures, making the "mild" winter more, rather than less, stressful to the insect.

Wood-feeding and other log-dependent cockroaches (Table 3.2) are sensitive to the ecological changes brought about by both modern forestry and human settlement and, like many saproxylic arthropods (Grove and Stork, 1999; Schiegg, 2000), may be used as habitat continuity indicators in ecological assessment. These insects rely on a resource whose removal from the ecosystem is the usual objective of forest management (Grove and Stork, 1999) and compete with lumber companies (Cleveland et al., 1934) and resident humans who prize coarse woody debris as fuel and building material. Wood-feeding cockroaches may survive canopy removal and subsequent desiccating conditions if logs of a size sufficient to provide a suitable microhabitat are left on the ground. Cryptocercus primarius, for example, has been collected from large-diameter logs in young re-growth forest in China (Fig. 10.5). More often, however, coarse woody debris left on the forest floor after logging operations is gathered and used as fuel (Nalepa et al., 2001b). Based on the work of Harley Rose (University of Sydney), the endemic Lord Howe Island wood-feeding cockroach Panesthia lata was recently listed by the New South Wales Scientific Committee as an endangered species (Adams, 2004). It has not been found on Lord Howe Island since the 1960s, probably because of rats introduced in 1918. Small numbers of the cockroach were recently discovered on Blackburn Island and Roach Island.

Litter-dwelling cockroaches can be sensitive habitat indicators. The Russian cockroach Ectobius duskei, normally found at levels of up to 10 individuals/m2 in undisturbed steppe, disappears if these grasslands are plowed to grow wheat. If the fields are allowed to lie fallow, the cockroaches gradually become reestablished (Bei-Bienko, 1969,1970). Although the species has been eliminated in intensely cultivated areas, a 1999 study found E. duskei well represented in the leaf litter of steppe meadows in the Samara district (Lyubechanskii and Smelyanskii, 1999).

The effect of disturbance on litter invertebrates depends not only on the type of disturbance, but also on site-specific factors. In the dry Mediterranean-type climate of western Australia cockroaches appear resilient to moderate disturbances. Cockroach numbers and species richness as measured by pitfall traps declined significantly after logging and fire, yet recovered within 48 mon.

Fig. 10.5 Li Li, Chinese Academy of Science, Kunming, and Wang De-Ming, Forest Bureau, Diqing Prefecture, opening a rotted log containing Cryptocercus primarius in a young re-growth spruce and fir forest at Napa Hai, Zhongdian Co., Yunnan Province, China. The cockroaches were found in large logs left on the forest floor after the forest was harvested; maximum regrowth was 10 cm in diameter. This site was immediately adjacent to a mature coniferous forest with logs also harboring the cockroach. Photo by C.A. Nalepa.

Fig. 10.5 Li Li, Chinese Academy of Science, Kunming, and Wang De-Ming, Forest Bureau, Diqing Prefecture, opening a rotted log containing Cryptocercus primarius in a young re-growth spruce and fir forest at Napa Hai, Zhongdian Co., Yunnan Province, China. The cockroaches were found in large logs left on the forest floor after the forest was harvested; maximum regrowth was 10 cm in diameter. This site was immediately adjacent to a mature coniferous forest with logs also harboring the cockroach. Photo by C.A. Nalepa.

The insects showed no significant response to habitat fragmentation and livestock activity, but were most diverse where forest litter was thickest. The authors explain their results in terms of the fire ecology of the area. In seasonally dry habitats cockroaches appear to have a high degree of tolerance to recurrent disturbances and may aes-tivate in burrows or under bark during harsh conditions (Abenserg-Traun et al., 1996b; Abbott et al., 2003). There is a distinction, however, between cockroaches adapted to these habitats and those residing where the ecological equilibrium is much more precarious. Tropical rainforests, where the vast majority of cockroaches live, are under heavy assault (Wilson, 2003), and large numbers of described and undescribed species are being lost along with the natural greenhouses in which they dwell. Grand-colas, for example, estimated 181 cockroach species in a lowland tropical forest in French Guiana, with 67 species active in the understory during night surveys in one site (Grandcolas, 1991,1994b). David Rentz (pers. comm. to CAN) has recorded 62 species of cockroaches, mostly blattellids, from his 0.65 ha of rainforest in Kuranda, Queensland (elev. 335 m asl). In one light trap study in Panama, 42% of 164 species captured were new to science (Wolda et al., 1983).

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