Track analysis of the species of Agrodes and Plochionocerus (Coleoptera: Staphylinidae)

Análisis de trazos de las especies de Agrodes y Plochionocerus (Coleoptera: Staphylinidae)

Julieta Asiain¹, Juan Márquez¹ and Juan J. Morrone^{2 *}

¹ Laboratorio de Sistemática Animal, Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de Hidalgo. Apartado postal 1–69, Plaza Juárez, 42001 Pachuca, Hidalgo, México.

^*Correspondent:
juanmorrone2001@yahoo.com.mx

Recibido: 24 enero 2009
Aceptado: 09 julio 2009

Abstract

The geographical distributions of 2 species of Agrodes and 13 species of Plochionocerus were analyzed using a panbiogeographic approach to identify their biogeographic patterns. Nine species have been recorded as being exclusively from South America, 2 exclusively from Central America, and 4 are shared between both areas. Two species of Agrodes and 3 of Plochionocerus are widely distributed in 2 or more subregions of the Neotropical region, and 6 species of Plochionocerus have more restricted distributions, basically ranging in a single subregion, and 4 species are restricted to a small number of localities. Three generalized tracks were identified in the Mesoamerican dominion of the Caribbean subregion, in the northwestern South American dominion of the Caribbean subregion, and in the Amazonian subregion. Species of other staphylinid genera provide additional support to these tracks.

Resumen

Se analizó la distribución geográfica de 2 especies de Agrodes y 13 especies de Plochionocerus utilizando un enfoque panbiogeográfico, con la finalidad de identificar sus patrones biogeográficos. De las especies analizadas, 9 han sido registradas exclusivamente para América del Sur, 2 exclusivamente para América Central y 4 son compartidas entre ambas áreas. Dos especies de Agrodes y 3 de Plochionocerus están distribuidas en 2 o más subregiones de la región Neotropical, 6 especies de Plochionocerus poseen distribuciones más restringidas, distribuyéndose básicamente en una sola subregión, y 4 especies se restringen a unas pocas localidades. Se identificaron 3 trazos generalizados en el dominio Mesoamericano de la subregion Caribeña, en el dominio Sudamericano Noroccidental de la subregión Caribeña y en la subregión Amazónica. Algunas especies de otros géneros de estafilínidos brindan soporte adicional a estos trazos.

Palabras clave: Xantholinini, panbiogeografía, trazos generalizados, región Neotropical.

Introduction

Agrodes Nordmann, 1837 and Plochionocerus Dejean, 1833 have been subjected to recent taxonomic revision (Asiain et al., 2007). Species assigned to these genera have metallic blue, purplish, green, and golden coloration, and a relatively elongate body. As a result of their systematic revision, several synonyms were detected, mainly for species of Plochionocerus, which currently comprises 18 species. Additionally, Agrodes, a former synonym of Plochionocerus, was resurrected and now includes 2 species. Recent phylogenetic analysis showed that both genera are monophyletic and sister taxa, and together constitute the sister group of Renda Blackwelder, 1952. Phylogenetic relationships among their species, however, are still poorly resolved (Asiain et al., 2007). Species of Agrodes and Plochionocerus, which are predators and apparently good flyers, mostly inhabit cloud and tropical forests, from 100 to 2 800 m. These species are distributed in the Neotropical region, from Mexico to Argentina.

We apply herein a panbiogeographic analysis to contribute to the knowledge of their distributional patterns and to compare them with the patterns of other Neotropical staphylinids.

We analyzed distributional data of 2 species of Agrodes and 13 out of the 18 species of Plochionocerus from Asiain et al. (2007), excluding 5 species with only 1 locality record (P. gracilis, P. hermani, P. modestus, P. reticularis and P. transversalis). We added the first record for Honduras of P. discedens (HONDURAS: Cortés: Cofradía, 25 km N P.N. Cusuco, 1 550 m, 26.viii.15–ix.1994, cloud forest/ FMND 94–41, flight intercept trap 1, S. and J. Peck 94–59 FIELD MUS. NAT. HIST/ NB: Probably more specimens in alcohol at FMNH/ Renda det. Newton 1995/ Plochionocerus discedens Asiain and Márquez 2008 det.).

The panbiogeographic method (Croizat, 1958, 1964) consists of plotting distributions of species on maps, and connecting their localities together via minimum distance lines to obtain individual tracks. The overlap of the individual tracks of several species allows the identification of generalized tracks, which indicate the pre–existence of ancestral biotic components that have been fragmented by tectonic or climatic changes (Croizat, 1958, 1964; Craw et al., 1999; Morrone, 2004, 2009). Some country records without precise locality data were indicated with a question mark. The generalized tracks were obtained based on the congruent overlap of the individual tracks.

Results

The geographical distribution and individual tracks of the species of Agrodes and Plochionocerus are shown in figures 1–10. Nine species have been recorded exclusively from South America, 2 exclusively from Central America and 4 are shared between both areas. Agrodes conicicollis is recorded from Ecuador, Peru and Brazil, whereas A. elegans is recorded from Nicaragua, Costa Rica, Panama, Colombia, Ecuador, Peru, Bolivia, and Brazil. Considering all species of Plochionocerus (18), Peru and Venezuela are the countries with the highest number of species, with 6 species each. They are followed by Costa Rica, Panama, Colombia, and Ecuador (5 species); Brazil (4 species); Bolivia and French Guyana (3 species); Mexico, Guatemala, El Salvador, Honduras, and Nicaragua (2 species); and Guyana, Surinam, Trinidad and Tobago, and Argentina (1 species). Two species of Agrodes and 3 of Plochionocerus are widely distributed in 2 or more subregions of the Neotropical region. Six species of Plochionocerus have more restricted distributions, basically being found in a single subregion. Four species of Plochionocerus are restricted to a few localities (Table 1, Figs. 1–10). The distribution of the species according to the regionalization of Latin America (sensu Morrone, 2006) is summarized in Table 1.

Based on the 15 individual tracks (Figs. 1–10), 3 generalized tracks were identified (Fig. 11). Two are in the Caribbean subregion (1 in the Mesoamerican domain and other in the Northwestern South American domain) and a third in the Amazonian subregion (Morrone, 2006). Mesoamerican track. This track is based on individual tracks of Plochionocerus discendens (Fig. 5), P. puncticeps (Fig. 6), and partially supported by Agrodes elegans (Fig. 1), P. humeralis (Fig. 9), P. marquezi (Fig. 2), and P. simplicicollis (Fig. 7).

Northwestern South American track. This track fell within the northwestern South American dominion of the Caribbean subregion. It is based on the individual tracks of Agrodes conicicollis (Fig. 2), Plochionocerus ashei (Fig. 1), P. impresipennis (Fig. 10), P. pronotalis (Fig. 3), and partially supported by A. elegans (Fig. 1), P. fulgens (Fig. 8), P. humeralis (Fig. 9), P. marquezi (Fig. 2), and P. simplicicollis (Fig. 7).

Amazonian track. This track falls within the Amazonian subregion, and is based on the individual tracks of Plochionocerus igneus (Fig. 3) and P. splendens, and partially supported by Agrodes conicicollis, A. elegans and P. fulgens (Fig. 8).

The geographical distribution of Plochionocerus newtonorum (Fig. 1) and P. janthinus (Fig. 4) does not coincide with any of the generalized tracks obtained. No nodes (areas of mixed biotic affinities) were found.

Discussion

Other staphylinid taxa that support the Mesoamerican track are 22 species of Homalolinus, 1 species of Heterolinus Sharp, 1885 and 7 species of Misantlius Sharp, 1885 (Asiain and Márquez, 2003; Márquez and Morrone, 2003). Márquez and Morrone (2003) distinguished a northern and a southern generalized track within the Mesoamerican dominion, based on an analysis of species of Homalolinus and Heterolinus, with the Nicaraguan lowlands representing the boundary between them. Species of Plochionocerus, Agrodes and Misantlius seem to support this hypothesis. The northern Mesoamerican track is supported by 9 species of Homalolinus (H. affinis, H. atronitens, H. confusus, H. mexicanus, H. minensis, H. obsoletus, H. rufopygus, H. sanguineus, and H. scutellaris) and 6 species of Misantlius (M. aequalis, M. carinulatus, M. hondurensis, M. optatus, M. rufipennis, and M. torquatus). The southern Mesoamerican track is supported by 3 species of Plochionocerus (P. humeralis, P. marquezi, and P. puncticeps), 12 species of Homalolinus (H. apiciventris, H. brevipennis, H. canaliculatus, H. dificilis, H. gracilis, H. mordax, H. planus, H. punctipennis, H. ruficollis, H. setosus, H. sharpi, and H. tripunctatus), Agrodes elegans, Misantlius gebieni, and Heterolinus basiniger (Asiain and Márquez, 2003; Márquez and Morrone, 2003; Navarrete–Heredia, 2005; Asiain et al., 2007).

The lowlands of Nicaragua seem to represent a biogeographic barrier for montane insect fauna, as previously noted by Halffter (1987). The emergence of these lowlands can be also interpreted as a vicariant event fragmenting a previously continuous distribution of several taxa, as is the case for some of the staphylinid beetles herein analyzed. The highest number of species of Plochionocerus is found in South America and the highest number of species of Homalolinus in Central America. Both genera include species that probably did not speciate after the vicariant event or events that fragmented the Mesoamerican and South American generalized tracks, namely Plochionocerus discedens, P. simplicicollis and Homalolinus divisus. Species from other staphylinid taxa supporting the northwestern South American track are Homalolinus aequatorialis, H. canaliculatus, Heterolinus basiniger, H. puncticeps and H. xanthogaster (Márquez and Morrone, 2003). No species of Misantlius, Homalolinus and Heterolinus support the Amazonian track.

Acknowledgements

We thank Mark Olson and 2 anonymous reviewers for their important suggestions to this work.

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