626 The effect of landscape structure and habitat composition on the presence of the threatened parasitic sand-living beetle Apalus bimaculatus (Coleoptera: Meloidae) Lina Ahlba¨ck,1 A˚ sa Berggren Abstract—Apalus bimaculatus (Linnaeus) (Coleoptera: Meloidae) is a beetle currently managed for conservation in Sweden. The species inhabits at-risk ephemeral and patchily distributed sandy habitats. However, little is known about its ecology and the factors important for its distribution. We censused 158 discrete sand patches within 31 potential sites for A. bimaculatus and examined which environmental variables predicted the probability of finding the beetle. Apalus bimaculatus was found at 17 sites, its presence at sand-patch scale was positively correlated with sand-patch area, sand temperature, and medium-sized sand grains. Although the beetle is assumed to be a parasite on the solitary bee, Colletes cunicularius (Linnaeus) (Hymenoptera: Colletidae), presence of the bee was a very weak predictor for A. bimaculatus, while other sand-living Hymenoptera were a strong predictor. At site-level scale, the beetle was positively correlated with total amount of sandy habitat and presence of sand-living Hymenoptera. Our study suggests that management strategies for this species should not consider sandy habitats equally. Rather, management efforts should focus on maintaining sites with larger total sandy areas, creating larger sand patches with medium-grained sand and a high degree of sun exposure. We also highlight that biotic interactions between the beetle and sand-living Hymenoptera are still poorly understood but potentially important for successful A. bimaculatus management. Re´sume´—Apalus bimaculatus (Linnaeus) (Coleoptera: Meloidae) est un cole´opte`re de Sue`de qui fait actuellement l’objet d’une gestion spe´ciale pour assurer sa conservation. L’espe`ce habite des milieux sablonneux e´phe´me`res qui sont a` risque et sont re´partis en taches. On connaıˆt cependant peu son e´cologie et les facteurs de´terminants de sa re´partition. Nous avons inventorie´ 158 taches sablonneuses discre`tes re´parties dans 31 sites potentiels a` la recherche d’A. bimaculatus et de´ter- mine´ quelles variables environnementales permettaient de pre´dire la probabilite´ de la pre´sence du cole´opte`re. Apalus bimaculatus ae´te´ retrouve´ dans 17 sites et sa pre´sence a` l’e´chelle de la tache sablonneuse est en corre´lation avec la surface de la tache sablonneuse, la tempe´rature du sable et la pre´sence de grains de sable de taille moyenne. Bien qu’on pre´sume que le cole´opte`re est un parasite de l’abeille solitaire Colletes cunicularius (Linnaeus) (Hymenoptera: Colletidae), la pre´sence de l’abeille est une faible variable pre´dictive de la pre´sence d’A. bimaculatus, alors que la pre´sence d’autres hyme´nopte`res are´nicoles est une forte variable pre´dictive. A` l’e´chelle des sites, la pre´sence du cole´opte`re est en forte corre´lation avec la quantite´ totale d’habitats sablonneux et la pre´sence d’hyme´nopte`res are´nicoles. Notre e´tude laisse croire que les strate´gies de gestion de cette espe`ce ne doivent pas tenir compte de tous les habitats sablonneux de manie`re e´gale. Au contraire, les efforts de gestion devraient eˆtre concentre´s sur le maintien des sites avec les plus grandes surfaces de zones sablonneuses et la cre´ation de taches sablonneuses plus grandes avec du sable de granulome´trie moyenne et une forte exposition au soleil. Nous soulignons aussi que les interactions biotiques entre le cole´opte`re et les hyme´nopte`res are´nicoles restent encore mal comprises, bien qu’elles soient potentiellement importantes pour une gestion re´ussie d’A. bimaculata. Received 20 September 2012. Accepted 20 December 2012. First published online 28 August 2013. L. Ahlba¨ck,1 A˚ . Berggren, Department of Ecology, Swedish University of Agricultural Sciences, PO Box 7044, SE-75007 Uppsala, Sweden 1Corresponding author (e-mail: [email protected]). Subject editor: Keith Summerville doi:10.4039/tce.2013.43 Can. Entomol. 145: 626–638 (2013) ᭧ 2013 Entomological Society of Canada Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.234, on 24 Sep 2021 at 18:31:54, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.4039/tce.2013.43 Ahlba¨ ck and Berggren 627 Introduction Apalus bimaculatus resides in the sub- terranean nests of its host species from the larval Degradation of natural landscapes has led to to the adult stage, where it feeds on food col- habitat loss and fragmentation that can negatively lected by the host (Notini 1942). It is believed affect the species that inhabit these areas (Fahrig that A. bimaculatus in Sweden is dependent on 1997, 2001; Marzluff and Ewing 2001; Baker and the solitary bee species Colletes cunicularius Harris 2007). Life history traits such as high (Linnaeus) (Hymenoptera: Colletidae) for its specialisation, poor dispersal, patchy distributions, persistence (Cederberg 2003). This bee also and/or an aggregated and seasonal appearance are uses sandy habitats for its breeding chambers linked to increased extinction risk when land- (Larsson and Tengo¨ 1989), which are aggregated scapes are degraded (McKinney 1997; Reinhardt in sub-populations and located several cm et al. 2005). Thus, the ecology and distribution of below the surface (Lo¨nnell and Edelsjo¨ 2004); a species form the foundation of its threat however, it is not clear if the beetle also uses assessments – one example being the International other sand-living bee species as hosts (Notini Union for Conservation of Nature red list (Inter- 1942; Frycklund 2006). national Union for Conservation of Nature 2012). Because the adult beetle is a poor flyer (Notini In Sweden, 804 insect species are currently 1942; Lo¨nnell and Edelsjo¨ 2004), it has been classified as threatened (vulnerable, endangered, suggested that A. bimaculatus, as with other or critically endangered) on the national red list, species belonging to the family Meloidae, use with the most common criteria for a taxon being phoresy – i.e., where one organism ‘‘hitches a included is that the distribution is small, largely ride’’ on another for the purpose of dispersal fragmented, or only exist in few localities (Bologna and Pinto 2001; Saul-Gershenz and (Ga¨rdenfors 2010). The species that specialise in Millar 2006; Bologna et al. 2008). Support ephemeral habitats, prone to change because of for this comes from Notini (1942), who showed natural successional processes, are vulnerable to that A. bimaculatus behaviourally orient to local extinctions; especially if these species are substances secreted from C. cunicularius.The poor dispersers (Warren 1991; Ranius 2000). dispersal of A. bimaculatus may therefore be One such species is the European beetle closely linked to the dispersal of C. cunicularius, Apalus bimaculatus (Linnaeus) (Coleoptera: further increasing the vulnerability of this spe- Meloidae) (Lundberg 1995; Fauna Europaea cies to the presence of a healthy host population. 2011). Apalus bimaculatus inhabits open sandy Thus, the distribution and dispersal ability of areas (Lo¨nnell and Edelsjo¨ 2004), a habitat that A. bimaculatus are likely to be linked to the has declined in Northern Europe following distribution and dispersal behaviour of its host, changes in land use where a reduction in grazing suggesting that landscape variables influencing and forest fires has promoted re-vegetation of the distribution of C. cunicularius (or other sand- these areas (Emanuelsson 2009). Unless active living bee species) are important for predicting vegetation removal is carried out, this habitat the presence of A. bimaculatus. usually becomes over-grown and unsuitable for To combat threats to A. bimaculatus popula- sand-living beetles within a decade (Lo¨nnell and tions in Sweden, the Swedish Environmental Edelsjo¨ 2004; Lo¨nnberg and Jonsell 2012). Thus, Protection Agency has established a species the habitat specialisation of A. bimaculatus has conservation management program (Lo¨nnell resulted in this species having a highly frag- 2010). Since 2004, management has focused on mented distribution in central and southwest habitat restoration by removing vegetation from Sweden (Cederberg 2003, Lo¨nnell and Edelsjo¨ sandy habitats in the distribution area of the 2004; Lo¨nnell 2005). Because of this, its current beetle. The aim is to expose the sandy substrate ‘‘near threatened’’ status on the Swedish red list and to reduce the shading to increase the avail- is expected to be upgraded to vulnerable if the able warm habitat that encourages establishment current habitat of ,2000 km2 continues to or persistence of the beetle. These actions are degrade through succession (Ga¨rdenfors 2010). based on national expert knowledge, but little is It is currently extinct in Finland (Lo¨nnell 2010) actually known about the species ecology and and Estonia (eBiodiversity 2012). behaviour, its dispersal and habitat requirements, ᭧ 2013 Entomological Society of Canada Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.234, on 24 Sep 2021 at 18:31:54, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.4039/tce.2013.43 628 Can. Entomol. Vol. 145, 2013 as very few studies have been carried out in is one of the first bees to emerge during the Northern Europe (but see Notini 1942; Lo¨nnell Swedish spring (Peakall and Schiestl 2004) and 2010). The current management of the species is active mainly between March and May (Notini therefore relies on a limited amount of infor- 1942). In addition to C. cunicularius, there are at mation of the species requirements. least 10 other Hymenoptera families (including Thus, the objective of this study is to examine members from all families within Apoidea and which landscape and habitat factors influence some taxa within Vespoidea, Chrysidoidea, and the distribution of A.