Does reduced mobility through fragmented landscapes explain patch extinction patterns for three honeyeaters?

Abstract

Summary 1.Habitat loss and associated fragmentation are major drivers of biodiversity decline, and understanding how they affect population processes (e.g. dispersal) is an important conservation goal. In a large-scale test employing 10 9 10 km units of replication, three species of Australian birds, the fuscous honeyeater, yellow-tufted honeyeater and white-plumed honeyeater, responded differently to fragmentation. The fuscous and yellow-tufted honeyeaters are 'decliners' that disappeared from suitable habitat in landscapes where levels of tree-cover fell below critical thresholds of 17 and 8%, respectively. The white-plumed honeyeater is a 'tolerant' species whose likelihood of occurrence in suitable habitat was independent of landscapelevel tree-cover. 2. To determine whether the absence of the two decliner species in low tree-cover landscapes can be explained by reduced genetic connectivity, we looked for signatures of reduced mobility and gene flow in response to fragmentation across agricultural landscapes in the Box-Ironbark region of north-central Victoria, Australia. 3. We compared patterns of genetic diversity and population structure at the regional scale and across twelve 100 km 2 landscapes with different tree-cover extents. We used genetic data to test landscape models predicting reduced dispersal through the agricultural matrix. We tested for evidence of sex-biased dispersal and sex-specific responses to fragmentation. 4. Reduced connectivity may have contributed to the disappearance of the yellow-tufted honey-eater from low tree-cover landscapes, as evidenced by male bias and increased relatedness among males in low tree-cover landscapes and signals of reduced gene flow and mobility through the agricultural matrix. We found no evidence for negative effects of fragmentation on gene flow in the other decliner, the fuscous honeyeater, suggesting that undetected pressures act on this species. As expected, there was no evidence for decreased movement through fragmented landscapes for the tolerant white-plumed honeyeater. 5. We demonstrated effects of habitat loss and fragmentation (stronger patterns of genetic differentiation, increased relatedness among males) on the yellow-tufted honeyeater above the threshold at which probability of occurrence dropped. Increasing extent and structural connectivity of habitat should be an appropriate management action for this species and other relatively sedentary woodland specialist species for which it can be taken as representative.

Species‐ and sex‐specific connectivity effects of habitat fragmentation in a suite of woodland birds

“…1C; . We also expected more pronounced genetic responses to fragmentation for the more philopatric sex: males in all species (Mulder 1995, Doerr et al 2011, Debus and Ford 2012, Harrisson et al 2013, 2014 except the Grey Shrike-thrush (which has been inferred to have male-biased dispersal; Pavlova et al 2012) and the Spotted and Striated Pardalotes (for which there was no evidence of sex-biased dispersal; Harrisson et al 2012). Sex-biased effects of fragmentation were expected to be particularly marked in the obligate cooperative breeders among the target species (Superb Fairy-wren and Brown Treecreeper), in which male offspring often stay as helpers at the nest, and to some degree in the facultative cooperative breeder (Eastern Yellow Robin).…”

“…(D) Using expert opinion and available biological data, Amos et al (2012) built numerous species-specific, spatially explicit prior models of gene flow through fragmented landscapes in Circuitscape; from these models, pairwise per-site landscape resistance distances representing IBD or IBR were calculated (here, different IBR models have been reduced to the single category for simplicity, but see Appendix G). (E) Birds of the 10 species were genotyped for microsatellites and other length-variable markers and were sexed following Harrisson et al (2012Harrisson et al ( , 2013Harrisson et al ( , 2014 and Pavlova et al (2012Pavlova et al ( , 2013; genetic distances (pairwise per-individual distances, GD; or per-site population F ST ) were calculated. (F) Mantel tests were used to test whether geographic distances (IBD) or landscape resistances (IBR) explained differentiation in genetic distances (GD or F ST ).…”

Field of Dreams: Restitution of Pollinator Services in Restored Bird‐Pollinated Plant Populations

“…menziesii . Although birds are still relatively abundant in our system, a reduced abundance of birds and pollinators in general (Potts et al ) due to for example habitat fragmentation (Davis et al ), introduced predators (Innes et al ), introduced honeybees (Paton ), or reduced dispersal (Harrisson et al ), will clearly impact on the potential for pollinator recovery into restored sites.…”

Biased parasitoid sex ratios:Wolbachia, functional traits, local and landscape effects

“…Habitat size may be small due to habitat loss and fragmentation (Fahrig, 2003) and may increase isolation by distance (Amos et al, 2014). Our knowledge on how fragmentation affects ASR is limited and comes largely from vertebrate systems (Harrisson, Pavlova, Amos, Radford, & Sunnucks, 2014; Reid et al, 2014), but insects with short generation times present an ideal opportunity to study these questions (Murphy, Battocletti, Tinghitella, Wimp, & Ries, 2016).…”