Plos ONE 10(5): E0125847
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RESEARCH ARTICLE Hitting an Unintended Target: Phylogeography of Bombus brasiliensis Lepeletier, 1836 and the First New Brazilian Bumblebee Species in a Century (Hymenoptera: Apidae) José Eustáquio Santos Júnior1, Fabrício R. Santos1, Fernando A. Silveira2* 1 Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 2 Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil * [email protected] OPEN ACCESS Abstract Citation: Santos Júnior JE, Santos FR, Silveira FA (2015) Hitting an Unintended Target: Phylogeography This work tested whether or not populations of Bombus brasiliensis isolated on mountain of Bombus brasiliensis Lepeletier, 1836 and the First tops of southeastern Brazil belonged to the same species as populations widespread in low- New Brazilian Bumblebee Species in a Century (Hymenoptera: Apidae). PLoS ONE 10(5): e0125847. land areas in the Atlantic coast and westward along the Paraná-river valley. Phylogeo- doi:10.1371/journal.pone.0125847 graphic and population genetic analyses showed that those populations were all Academic Editor: Sean Brady, Smithsonian National conspecific. However, they revealed a previously unrecognized, apparently rare, and poten- Museum of Natural History, UNITED STATES tially endangered species in one of the most threatened biodiversity hotspots of the World, Received: September 18, 2014 the Brazilian Atlantic Forest. This species is described here as Bombus bahiensis sp. n., and included in a revised key for the identification of the bumblebee species known to occur Accepted: March 25, 2015 in Brazil. Phylogenetic analyses based on two mtDNA markers suggest this new species to Published: May 20, 2015 be sister to B. brasiliensis, from which its workers and queens can be easily distinguished Copyright: © 2015 Santos Júnior et al. This is an by the lack of a yellow hair-band on the first metasomal tergum. The results presented here open access article distributed under the terms of the are consistent with the hypothesis that B. bahiensis sp. n. may have originated from an an- Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any cestral population isolated in an evergreen-forest refuge (the so-called Bahia refuge) during medium, provided the original author and source are cold, dry periods of the Pleistocene. This refuge is also known as an important area of ende- credited. mism for several animal taxa, including other bees. Secondary contact between B. bahien- Data Availability Statement: All original molecular sis and B. brasiliensis may be presently prevented by a strip of semi-deciduous forest in a data were made available in GenBank (accession climate zone characterized by relatively long dry seasons. Considering the relatively limited numbers available in Table 1). Accession numbers for data collected from GenBank and BOLD Systems are range of this new species and the current anthropic pressure on its environment, attention available in Table 2. should be given to its conservation status. Funding: This study was suported by grants from the Fundação de Amparo à Pesquisa de Minas Gerais (http://www.fapemig.br/) to FAS and Conselho Nacional de Pesquisas (http://www.cnpq.br/) to FRS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. PLOS ONE | DOI:10.1371/journal.pone.0125847 May 20, 2015 1/21 Bumblebee Phylogeography and New Species Competing Interests: The authors have declared Introduction that no competing interests exist. Despite the fact that, taxonomically, bees are among the best known insects in the world (for example [1]), there are taxonomic problems to be solved in the group, including sex association in dimorphic species and distinction of cryptic species, even in relatively well-known taxa. In these cases, molecular data, including the so called DNA barcode, alone or integrated to other types of characters, have proven to be much useful (for example [2, 3]). The bumblebees (genus Bombus Latreille, 1802) comprise approximately 250 species widely distributed in the world, but occurring mainly in the cool subtropical and temperate areas of the Nearctic and, especially, Palearctic regions [4]. Defining species limits in Bombus is fre- quently difficult, because of the lack of useful structural characters and the great variability in hair-color patterns. This has led to an array of recent studies employing DNA markers to eluci- date bumblebee-species boundaries (for example [5–12]). Molecular tools have also been used in the genus to investigate intraspecific genetic structure, phylogeography and phylogenetic re- lationships (for example [13–22]). In South America, most of the species of Bombus are distributed along the Andes and in temperate regions, with only a few species recorded in the warm lowlands—the later, actually, the only bumblebees to occur in such environments in the world [1]. Only six species of the genus are generally referred to occur in Brazil [23], all belonging to the same subgenus—Fervi- dobombus Skorikov, 1922 or Thoracobombus Dalla Torre, 1880, depending on which classifica- tion one adopts (for example [1, 24]or[25]). Five of these species (B. bellicosus Smith, 1879; B. brasiliensis Lepeletier, 1836; B. brevivillus Franklin, 1913; B. pauloensis Friese, 1913; and B. transversalis (Olivier, 1789)) seem to be very closely related, while the sixth one, B. morio (Swe- derus, 1787) belongs to a distinctive clade in the same subgenus [19, 21]. Bombus pauloensis has been widely treated as B. atratus Franklin, 1913 in the literature (for an explanation for the adoption of B. pauloensis as a valid name, see [24]). The occurrence of a seventh species in western Brazil, B. pullatus Franklin, 1913, was reported by Milliron [26], but considered with suspicion by Abrahamovich & Díaz [27], and ignored by Moure & Melo [24], and needs confir- mation. An eighth species, B. rubriventris Lepeletier, 1836, was recorded with doubts by Milli- ron [26] as possibly occurring in the state of Goiás. According to him, this species, known only from its female holotype, would be very rare or extinct. One cannot rule out the possibility that the assignment of B. rubriventris to Brazil resulted from mere labeling mistake or from wrong interpretation of the type locality (see [26] for details). In their thorough revision of the Brazilian bumblebees, Moure & Sakagami [23]) noted that B. brasiliensis Lepeletier, 1836 was the only species to be more common on mountaintops (mainly in the ranges along the southern and eastern Brazilian coasts) than in lowlands, and that it was the only one recorded in elevations above 1,800 m. Later, Silveira & Cure [28] noted that B. brasiliensis is absent in the lowlands surrounding the mountain ranges where it is rela- tively common further inland in southeastern Brazil. The occurrence of these isolated moun- taintop populations of B. brasiliensis raised the suspicion that they might in fact belong to a species different from the one present in the lowlands along the coast and in the Paraná River valley. Here, this hypothesis is tested, mainly by means of phylogenetic and population-genetic analyses of two mtDNA genes. Since the question of how to delimit species boundaries is still in debate (see, for instance, the revision by Wiley & Lieberman [29]), different character sources (molecular and morphological) and analytical methods (tree and non-tree based) were complementarily employed to decide whether or not a set of populations should be considered as a new taxon. PLOS ONE | DOI:10.1371/journal.pone.0125847 May 20, 2015 2/21 Bumblebee Phylogeography and New Species Materials and Methods Morphological and Molecular Procedures The description of the new species presented below was based on six specimens—three workers and a queen from the municipality of Ilhéus, in the Brazilian state of Bahia, and two workers collected in the municipality of Conceição da Barra, state of Espírito Santo. These specimens are deposited at the Taxonomic Collections of the ‘Universidade Federal de Minas Gerais’— UFMG—and in the ‘Padre Jesus Santiago Moure’ entomological collection, of the ‘Universi- dade Federal do Paraná’—DZUP—, as detailed in the section “Taxonomic treatment”, below. Two collecting expeditions were conducted in southern Bahia and northern Espírito Santo states (coordinates of sampling sites are, in Bahia: Eunápolis—16°25'8"S, 39°34'55"W, 162m; Itamaraju—16°58'39"S, 39°33'16"W, 81m; Porto Seguro—16°27'3"S, 39°17'16"W, 114m; and, in Espírito Santo: Conceição da Barra—18°20'54"S,39°51'06"W, 47m; São Mateus—18°45'13"S, 39°51'39"W, 39 m; Sooretama—19°03'01"S, 40°08'02"W, 94m), under the collecting permit number 23784 (granted by “Instituto Chico Mendes de Conservação da Biodiversidade” to JESJ), in an attempt to increase molecular sample size and geographic representation. No addi- tional specimens were found, however, during these expeditions. The specimens were examined under a dissection microscope (Leica M125) and compared to the descriptions in Moure & Sakagami [23]. Comparisons were also made with photographs of the lectotype of B. brasiliensis Lepeletier, 1836, reproduced here in Fig 1A and 1B. Direct ob- servation of this type was not done because, after examining hundreds of specimens of B. brasi- liensis from all its geographic range, an easily-observable diagnostic character was found to distinguish the two concerned species, which could be readily checked in the photographs ob- tained from the type. Morphological terminology employed here is mostly that of Moure & Sakagami [23]. Flagellomeres are designated as F1, F2, F3 etc. Accordingly, metasomal terga and sterna are designated as T1, T2, T3 etc and S1, S2, S3 etc. The apical width of the malar area is the shortest width of the malar area, measured along the mandible base. Two mitochondrial markers, Cytochrome oxidase I (COI) and Cytochrome B (CytB) were employed in addition to the morphological characters.