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Author's personal copy Conserv Genet (2013) 14:511–528 DOI 10.1007/s10592-012-0436-9 RESEARCH ARTICLE Species-specific traits predict genetic structure but not genetic diversity of three fragmented Afrotropical forest butterfly species J. L. Bossart • Josephine B. Antwi Received: 21 June 2012 / Accepted: 3 December 2012 / Published online: 11 December 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract The Upper Guinean forests of Ghana, West very common species, with relaxed habitat fidelity, was Africa, are considered among the most threatened and genetically depauperate. There was limited evidence of fragmented in the world. Little is known about the genetic genetic erosion from the sacred groves despite these small consequences of fragmentation on Ghana’s forest-associ- forest patches accounting for less than 1–10 % of the total ated species, but this genetic signature is generally area of the forest reserves, which indicates these forest expected to differ across species. We compared patterns of relics have high conservation value. mtDNA cytochrome oxidase I (COI) variation of three Nymphalid forest butterfly species that differ with respect Keywords Sacred groves Á Habitat fragmentation Á to their relative dispersibilities (Aterica galene: high hab- Lepidoptera Á Ghana Á Nymphalidae Á mtDNA itat fidelity, low dispersal ability; Euphaedra medon: high habitat fidelity, strong dispersal ability; Gnophodes betsimena: relaxed habitat fidelity, low dispersal ability). Introduction Individuals were collected from two large forest reserves and five small sacred forest groves. Patterns of differenti- Habitat destruction and fragmentation due to human ation across species were broadly coincident with our activities is one of the most pervasive threats to global predicted hierarchy of relative species dispersibility and biodiversity (DeFries et al. 2005). It accounts either suggested that genetic connectivity is most compromised directly or indirectly for *90 % of all threatened and by strict fidelity to forest habitat rather than by raw endangered birds, mammals, and amphibians (IUCN capacity for sustained flight. Connectivity was uncorrelated 2012), and likely for as many of the less charismatic, less with geographic distance, but instead seemed best well-documented species. Habitat fragmentation converts explained by urbanization and the sequential pattern of formerly panmictic populations into subpopulations that forest loss. Genetic diversity was dramatically different are potentially isolated due to lack of dispersal and gene among species and not easily explained by either species- flow among them (Fahrig 2002, 2003; Frankham 2005). specific traits or effects of fragmentation. Aterica galene, Such isolation promotes loss of genetic diversity via the species most impacted by fragmentation, exhibited very genetic drift, inbreeding, and local adaptation (Avise 1994; high diversity, whereas G. betsimena, a broadly distributed, Saccheri et al. 1996, 1998; Reed and Frankham 2003; Trizio et al. 2005; Bickel et al. 2006). Local extinctions can ultimately result if isolated populations consequently lose & J. L. Bossart ( ) Á J. B. Antwi their genetic and/or demographic viability (Caughley 1994; Department of Biological Sciences, Southeastern Louisiana University, SLU 10736, Hammond, LA 70402, USA Fahrig 2002, 2003; Swift and Hannon 2010). e-mail: [email protected] Whether fragmented populations are genetically isolated depends on the multiple proximate (landscape-specific) and Present Address: ultimate (species-specific) factors that impact movement J. B. Antwi Department of Entomology, Texas A&M University, and gene flow among habitat patches. Of these, spatial College Station, TX 77843, USA distance between fragments has been, by far, the factor 123 Author's personal copy 512 Conserv Genet (2013) 14:511–528 evaluated most often. Because individuals are more able diverse (e.g. legal and illegal logging, fuel wood extraction, and likely to disperse among fragments that are closer out-of-control bush fires, mining pressures) and are nega- together versus those farther apart, genetic connectivity is tively impacting forest habitat both within and outside expected to decrease with increasing geographic distance designated reserve areas (Dei 1988; Odoom 2005; Osafo between patches (Wright 1943; Slatkin 1993). Straight-line 2005; Blay et al. 2009). distance, however, has often been found to be a poor pre- Of the five countries that constitute the Upper Guinean dictor of genetic connectivity (Jenkins et al. 2010), in part hotspot, Ghana is second only to Cote d’Ivoire in terms of because dispersal and gene flow among subpopulations forest lost. High canopy forest in the country comprises also depends on the composition and structure of the only 10–15 % of its original extent (Hawthorne and intervening landscape matrix (Debinski 2006; Hokit et al. Abu-Juam 1995) and spots the landscape as highly isolated 2010). The landscape that separates habitat patches is a patches embedded in an anthropogenically derived, farm- complex mosaic of vegetative communities and structural bush savanna matrix (Hawthorne and Abu-Juam 1995; features that influence emigration, and the rate and path- Poorter et al. 2004). The only substantial expanses way of dispersal through the matrix (Debinski 2006; remaining are the forest reserves that were set aside in the Haynes et al. 2007; Kuefler et al. 2010; Prevedello and late 1920s, and which are mostly managed for timber Vieira 2010). Ultimately, however, whether a landscape is production (Hawthorne and Abu-Juam 1995). Nearly no actually perceived as fragmented or not depends upon the intact forest habitat exists outside the gazetted reserves. specific species, and the traits and perceptions that define What little that does is in the form of thin shreds of riparian that species and how these explicitly integrate with attri- forest and the many sacred forest groves scattered across butes of the landscape (Finn et al. 2007; Louy et al. 2007; the landscape. Sacred groves are small forests (some are Habel et al. 2009). By definition, species with strict fidelity less than a hectare) that have persisted because of the to the habitat fragment will be spatially isolated regardless community-based, traditional belief systems that have of their raw physical capacity to disperse. Conversely, restricted access and use (Lebbie and Freudenberger 1996; species with even weak dispersal capabilities may retain Ntiamoa-Baidu 2001; UNESCO 2003). population connectivity if intervening matrix habitats are The extent to which deforestation has affected the perceived as relatively benign or otherwise acts as conduits region’s forest dependent species is largely unknown. of dispersal. Empirical data from study of the forest communities of Habitat loss and fragmentation is pervasive at all land- Western West Africa are rare. This pervasive knowledge scape scales and affects virtually all habitat types. How- gap prevents development of the science-based manage- ever, few ecosystems are currently being as extensively ment strategies that are the cornerstone of successful con- impacted as the world’s tropical forests, where this broad servation, weakens arguments for strengthened legislative scale landscape transformation also has the most significant protection, and further undermines an already tenuous implications for biodiversity. Tropical forests harbor more conservation framework. Although multiple governmental species than any other biome, many of which are narrowly and private conservation agencies are in place and oper- endemic (Myers et al. 2000). Deforestation, in general, ating within each country, socioeconomic priorities, and in results in the creation of an open, structurally simplified some cases civil strife, continue to thwart efforts to com- surrounding matrix, which amplifies the impacts of exter- pile these critical data. nal influences on the forest community and exacerbates the Here we investigate the effects of fragmentation and isolating effects of fragmentation. species’ dispersibility on the spatial genetic structure of Of the world’s tropical forests, those of the Upper three co-occurring, Afrotropical forest butterfly species Guinean sub-region of western West Africa are considered sampled from forest reserves and sacred forests groves in among the most threatened (Myers et al. 2000; Poorter Ghana. Our primary goal was to determine the extent and et al. 2004; FAO 2010). Africa, in general, is experiencing distribution of genetic variation within species, with an aim the highest rate of forest loss, and the Upper Guinean towards assessing the relative isolation of fragmented forests are being depleted at a faster rate than tropical populations and the conservation value of sacred groves as forest elsewhere on the continent (FAO 2010). Designation repositories of genetic diversity and as stepping stones of these forests as one of only 25 global biodiversity hot- facilitating connectivity across the landscape. We also spots reflects both the seriousness of the threat and the high expected that measures of diversity and isolation would levels of biodiversity and endemism found within their correlate with species-specific dispersibilities since a borders (Myers et al. 2000). Estimates vary as to how much higher likelihood of movement among fragments should be forest has literally been destroyed, but all indicate an manifest as both decreased genetic variation among pop- extensive and progressive loss of forest cover across the ulations