Oxycrepis Reiche, 1843

Kipling, Will, 2020, Phylogeny and classification of the genus-group taxa of Loxandrina (Coleoptera, Carabidae, Abacetini), Deutsche Entomologische Zeitschrift 67 (2), pp. 151-182 : 151

Genus Oxycrepis Reiche, 1843

Type species.

Oxycrepis leucocera Reiche, 1843: 78, by monotypy.

subgenus Loxandrus LeConte, 1853; type species Feronia recta Say, 1823: 58, designated by Casey (1918).

= Megalostylus Chaudoir, 1842 nec Schoenherr, 1840; type species Feronia recta Say, 1823 designated by Casey (1918: 325)

subgenus Adrimus Bates, 1872; type species Loxandrus viridescens Bates, 1871: 132, designated by Straneo (1977).

subgenus Metoncidus Bates, 1871; type species Metoncidus tenebrioides Bates, 1871: 134, by monotypy.

subgenus Stolonis Motschulsky, 1866; type species Stolonis notula Motschulsky, 1866: 231, by monotypy.

= Prostolonis Mateu, 1976; type species Prostolonis martinezi Mateu, 1976, by original designation. Synonymy by Allen and Ball (1980: 527)

Selected literature.

Review of some South American species ( Straneo 1991, 1993), treatments of North American species ( Allen 1972; Bousquet 2006), synopsis of Mexican species ( Allen and Ball 1980), new South American species ( Will and Liebherr 1997; Will 2004, 2008; Anichtchenko and Will 2009; Costa et al. 2011).

Described species and range.

Currently 244 species are described. The vast majority of species are found in tropical South America. The group extends south to at least southern Buenos Aires Province, Argentina, north through tropical South America, Central America, the Caribbean and eastern North America as far north as Ontario, Canada, in the southwest west to Arizona, USA and east to the Atlantic coast.

Adult morphology.

The most diverse genus in Loxandrina. Though most Oxycrepis species are very similar looking, with a body form generally similar to an average platynine or small pterostichine, the genus includes several highly divergent forms that have been described and recognized as genera. The most common form is well represented by, O. recta the type species of the subgenus Loxandrus (Fig. 4 ), which contrasts with species that have the pronotum decidedly narrow throughout, with the width equal to or less than the length, or very narrowly constricted at the base ( Oxycrepis s. str., Stolonis (Figs 6 , 7 )) and the distinctly parallel-sided forms ( Metoncidus (Fig. 8 )). A few species described in Adrimus and Loxandrus have a distinctive, relatively short, broad pronotum and more oval elytra with very large eyes (Fig. 5 ) ( Will and Liebherr 1997). Oxycrepis species range from small to medium size (3.2-15 mm). Most are black or piceous and some are castaneous or brown. Legs, mouthparts and the ventral surface of the body may be paler than the dorsal surface and legs are frequently strongly contrasting paler, flavous or orangish brown. In some species the distal or medial antennomeres are white and strongly contrasting with other, black or heavily infuscated antennomeres. In many species the elytra have variously arranged pale spots or vittae, paler first elytral intervals or a more or less well-defined paler region at the apex of the elytra (Fig. 6 ). Many are glossy and very often have a more or less prominent spectral iridescence. A smaller number are matt from a deeply impressed mesh microsculpture (e.g., O. opacula (Bates, 1871) and O. sculptilis (Bates, 1884)). The majority of species appear to have large and functional flight wings and flight to lights at night has been commonly observed. But significant reduction of the flight wings is known across the genus. The apex of the prosternal process is smooth and a raised margin, like what is common in Zeodera , is very rare, only known from one described species, Oxycrepis mirei (Straneo, 1991). The elytral plica is typically well-developed, but is often very small and narrow, or absent as in the species Allen and Ball (1980) assigned to the infimus group. Most species have a single discal puncture in the elytral interval 3 but Metoncidus , Stolonis and Oxycrepis s. str. frequently have additional elytral setae. Males of many species have notably asymmetrically expanded protarsomeres but unmodified or only subtly expanded protarsomeres occur in a few species from across the genus.

Life history notes.

These beetles are terrestrial, epigeal, usually found in moist to very wet habitats. They may be associated with standing or running water, though species in Central and South American rainforests can frequently be found far from water in very wet, closed canopy forests. They are nocturnally active, generalist predators that are frequently found in mixed species aggregations. I have collected as many as six species together under a single rock in localities in southeastern USA. Tropical species are frequently found at high density in areas with fallen flower-petals and/or fruits ( Paarmann et al. 2002, 2001; Will unpublished data).

Discussion.

Nominally seven genus-level taxa are subsumed in this clade. Of those, Megalostylus is a junior homonym of Megalostylus Schoenherr, 1840 ( Curculionidae ) and Prostolonis is currently considered a junior synonym of Stolonis . The other five have been considered generically distinct, but Oxycrepis s. str., Adrimus , Stolonis and Metoncidus are all derived from within a clade of New World species that were classified as Loxandrus by previous authors. This renders a concept of Loxandrus that includes all the New World species paraphyletic (Fig. 1 ). North American species that are included in the analysis form a clade sister to the remaining species, which appears consistent with recognition of Loxandrus s. str. as a genus. However, currently there is no satisfactory way to separate Oxycrepis (Loxandrus) species from Oxycrepis incertae sedis (see key, couplet 16). Given that many species cannot be confidently assigned to either the subgenus Loxandrus clade or the clade containing Oxycrepis s. str., the appropriate level to apply the genus based on evidence is the clade including the entire set of New World species. Therefore, Adrimus , Stolonis , Metoncidus and Loxandrus are herein treated as subgenera. Of the five genus-level taxa included, Oxycrepis has nomenclatural priority.

Allen (1972) revised most of the taxa in what is now the subgenus Loxandrus and this early effort was then further refined and expanded by Allen and Ball (1980) and then by Bousquet (2006). Bousquet defined nine species groups and provided character states for each. While the monophyly of these informal groups were not broadly tested, six of nine were included in the present study, three represented by more than one species; agilis group, celeris group, and erratica group. All of those groups were found to be monophyletic with high support (PP 1.0) and form a clade with the species representing the saphyrina and recta groups.

The species of these five groups are all included in the subgenus Loxandrus . They are all similar in general form and share a combination of character states. They are typically medium sized (5-13 mm), black or piceous, with legs, antennae, and mouthparts often paler, flavous or orangish brown. Elytra are uniformly dark or rarely have an orange spot near the apex. Many are somewhat or very glossy and have an obvious spectral iridescence, especially ventrally. The majority of species appear to have large and functional flight wings, but rarely the flight wings are reduced. Elytral interval 3 has a single puncture and the elytral plica is well-developed. Males have distinctly asymmetrically expanded protarsomeres. The metepisternum is long and apically rounded. The apex of the prosternal process does not have a raised margin. The mentum tooth does not reach the level of apices of lateral lobes and the paramedial pits are indistinct.

The subgenus Adrimus was initially established as a genus by Bates (1872) to include Loxandrus auct. species that have a very short, parallel-sided metepimeron. Bates also noted for those species where he had male specimens, that unlike species he included in Loxandrus , the protarsomeres were only slightly expanded and symmetrical. Straneo (1993) briefly discussed the taxonomic position of Adrimus and described 11 additional species. Straneo reiterated that the Adrimus species have males with symmetrically expanded protarsomeres (Fig. 3B ) and the metepimeron "very short and truncate at the apex" (Fig. 3D ). I have examined types or authoritatively identified specimens ( CMNH, MCSN, MNHN, EMEC) of all but six of the 23 species attributed to Adrimus and found that they vary in both of these characters. Four forms of the metepimeron are present among these species (Fig. 3C-F ; character 21): 1. Long, rounded, typical form in Oxycrepis ( O. latibasis (Straneo, 1993)); 2. Short rounded apex ( O. elytralis (Straneo, 1993)); 3. Very short parallel-sided, truncate (corresponding to descriptions of Bates and Straneo) in O. aenescens ( Tschitschérine, 1900), O. affinis ( Tschitschérine, 1900), O. gebi Will, O. fuscipes ( Brullé, 1835), O. longior (Straneo, 1993), O. xiproma Will, O. rasutulis Will, O. uruguaica ( Tschitschérine, 1903), O. ventralis (Straneo, 1993), O. rufangula (Bates, 1872), and O. viridescens (Bates, 1871); and 4. Short, triangular ( O. claripes (Straneo, 1993), O. iridea (Straneo, 1993), O. amatona Will, O. paulensis (Straneo, 1993).

Five Adrimus species are known only from the female holotype and for five others I have not examined males. Among the species I have examined male protarsomeres have three forms (Fig. 3A-B ; character 36): 1. symmetrical and slightly expanded ( O. crepera (Bates, 1872), O. fuscipes , O. gebi , O. iridea , O. microdera (Bates,1872), O. rasutulis ); 2. asymmetrical expanded, typical form as found in many typical Oxycrepis ( O. affinis , O. longior , O. uruguaicus , O. ventralis ); and 3. symmetrical and very narrowly expanded ( O. viridescens , O. claripes , O. amatona ).

There is no clear correlation of the states for the characters of the male protarsi and metepimeron. Oxycrepis (A.) viridescens was selected by Straneo (1977) as the type species for Adrimus . This species has both the very short, parallel-sided, truncate metepimera and symmetrical, slightly expanded male protarsomeres.

Unfortunately specimens of Adrimus -like species are rarely collected. I included only two species in my analysis from which I could extract DNA, one from Brazil and one from Colombia. Both are typical Adrimus in that they have a very short, truncate metepimeron. As these two are found to be most closely related to each other with very high support (PP 1.0, Fig. 1 ), and nest well within the Oxycrepis clade, Adrimus is treated as subgenus. As a working hypothesis, those species with any of the three short metepimeron states and those species not yet examined for the state of the metepimeron are included in the subgenus. As O. (A.) latibasis (Straneo, 1993) has a long rounded metepimeron it is moved to Oxycrepis incertae sedis.

Allen and Ball (1980) considered Oxycrepis s. str. as a close relative of Stolonis but recognized the four species included in Oxycrepis s. str. as a distinctive group of relatively large sized, hirsute species having an elongate-ovoid pronotal form. This is consistent with subsequent studies ( Will 2005) and the results found here, which place Oxycrepis s. str. sister to Stolonis including an undescribed Oxycrepis species that has some features of Straneo’s species group-17 ( Straneo 1991), such as bi-colored antennae. Only O. cordata Tschitschérine, 1900 was included in the current analysis, but I have also examined types or confidently identified material for O. leucocera Reiche, 1843 and O. brasiliensis Tschitschérine, 1900, which share the same form, patterns of setation, and most character states with O. cordata ( Will 2005).

Stolonis species are typically recognized by their narrowly constricted pronotal base and serrulate protibial spurs. This subgenus appears to be monophyletic but there is a great deal of variation and overlap in some characters with other Oxycrepis . Stolonis includes some species with bi-colored antennae and legs, states also found in Oxycrepis s. str. and Straneo’s group-17 species. A few Stolonis species have additional setae on elytral intervals 3, 5, and 7, such as is found in species of Metoncidus . Some species have the dorsal surface of the median lobe with a region of thin, translucent and almost membranous cuticle similar to what is found in some species of Adrimus . There is variation in pronotal shape, but all are notably basally narrowed, most are more or less prolonged beyond the level of the hind setae ( Will 2005). Until a more detailed study of the included species and their respective types is done, species described in Stolonis are retained in the subgenus.

Metoncidus is a small, exclusively South American subgenus that includes three species with a distinctive combination of character states including an elongate, parallel-sided form, relatively short antennae, male ventrite VI with four setae, and many setae on elytral intervals 3, 5, and 7. The species were recently treated ( Will 2004). Of the three species, only O. (M.) epiphytes was included in the analysis and this species was placed in a derived clade of South American Oxycrepis .

More than 150 species are placed in Oxycrepis incertae sedis. Informal groups of species that have been created in previous works are used to help organize these taxa by some notion of similarity (Suppl. material 1), but formal subgeneric classification based on synapomorphies will require detailed revisionary study.

Figures

Figure 1. Phylogeny of Loxandrina inferred from a Bayesian analysis of the combined dataset (analysis 3). Numbers at nodes are posterior probability values (PP). Stars at nodes mark clades found in a parsimony optimality analysis using the morphology partition. Diamonds at nodes mark recognized genera and subgenera inferred from a Bayesian analysis of the sequence data partition (analysis 2).

Figure 3. Protarsomeres and metepimera. Male left tibia and protarsomeres: A. Oxycrepis (Loxandrus) recta (Say). Asymmetrically expanded, as in typical many Loxandrina species; B. Oxycrepis (Adrimus) gebi Will narrow, symmetrically, slightly expanded. Metepimera, left side: C. Oxycrepis (Loxandrus) recta. Large, elongate, apically rounded form, as in typical Loxandrina species. Black outline added to emphasize shape; D. Oxycrepis (Adrimus) rasutulis Will. Rectangular, narrow, truncate form, black outline added to emphasize shape. Drawings of alternative metepimera shapes: E. short, apically rounded form; F. narrowly triangular, truncate form.

Figures 4 - 7. Habitus. 4. Oxycrepis (Loxandrus) recta (Say); 5. O. strigomeroides (Straneo); 6. O. & nbsp; elnae (Allen); 7. O. (Adrimus) rasutulis Will.

Figures 8 - 11. Habitus. 8. Oxycrepis (s. str.) cordata (Tschitscherine); 9. O. (Stolonis) tapiai (Will); 10. O. (Metoncidus) epiphyta (Will) (holotype); 11. Pediomorphus planiusculus Chaudoir.