A review of the genus Oosternum Sharp of the West Indies ( Coleoptera : Hydrophilidae : Sphaeridiinae )

The representatives of the genus Oosternum Sharp, 1882 occurring in the West Indies are revised. Ten species are recorded, of which seven are here described as new: Oosternum andersoni sp. n. (Cuba), O. bacharenge sp. n. (Dominican Republic), O. cercyonoides sp. n. (Jamaica), O. insulare sp. n. (Jamaica), O. luciae sp. n. (Saint Lucia), O. megnai sp. n. (Cuba) and O. pecki sp. n. (Dominican Republic). Diagnoses and detailed distributional data are also provided for O. sharpi Hansen, 1999 (widespread throughout both Greater and Lesser Antilles), O. latum Fikáček, Hebauer & Hansen, 2009 (endemic to St. Vincent) and an undescribed species from the Bahamas. A key to the West Indian Oosternum is provided and important diagnostic characters are illustrated. The West Indian fauna of Oosternum contains representatives of five different species groups and likely originated by multiple independent colonizations from the American continent. Within the study region, the highest diversity is known from the Greater Antilles, where two endemic species each in Cuba, Jamaica, and Hispaniola. The populations of O. sharpi were found to consist exclusively of females on all islands with the exception Puerto Rico. Key Words


Introduction
The West Indies (i.e. the Caribbean islands off the continental shelf ;Bond 1993) is a region generally known for its high species diversity and endemism.At the same time, large part of its natural habitats were destroyed and it is therefore considered as one of the world's biodiversity hotspots (Mittermeier et al. 2005).Although a large number of biodiversity studies have been conducted in the area, surprisingly little is known about the diversity of insects and other invertebrates.Cryptic leaf-litter inhabiting taxa are among those for which available information is especially limited, although a very high diversity Fikáček and Hebauer 2009;Fikáček et al. 2009;Makhan 2009;Short and Fikáček 2011) and additional ca.45 species are awaiting description (M.Fikáček unpubl.data).Based on the distribution data of the species groups which were already revised in detail (see aforementioned references), the genus includes both widely distributed species as well as those with very limited ranges, and seems therefore an ideal model group to study the biogeography and endemism of the leaf-litter invertebrates of the West Indian islands.This motivated us to perform its detailed taxonomic revision.
Available data from the West Indies were very scarce prior to this study.A single widespread species, O. sharpi Hansen, 1999, was recorded from Cuba and Puerto Rico (Peck 2005;Spangler 1981, in both cases as O. costatum Sharp, 1882) and the supposed single island endemic O. latum Fikáček, Hebauer & Hansen, 2009 was described recently from the Saint Vincent Island of the Lesser Antilles (Fikáček et al. 2009).For this study we have accumulated the material from 15 islands of both the Greater and Lesser Antilles, resulting from our own recent field work in Cuba and Jamaica and from several large projects by the Canadian and US entomologists.The results of the taxonomic revision of this material are summarized below.

Materials and methods
A total of 280 specimens from 13 countries (15 islands) of the West Indies were examined in this study.Most specimens were collected by sifting leaf litter in various kinds of forests with subsequent extraction using Berlese funnels and Winkler traps.Part of this material was collected during our recent expeditions to various parts of Cuba and Jamaica.The remaining material was examined from the Canadian and US collections, most importantly the personal collection of Professor Stewart Peck (SBPC) and the West Indian Beetle Fauna Project Collection (WICP).
Habitus photographs were taken using Canon EOS 550D digital camera with attached Canon MP-E65mm f/2.8 1-5× macro lens, and subsequently adapted in Adobe Photoshop CS5.Drawings of male genitalia are based on photographs taken using Canon EOS 1100D digital camera attached to Olympus BX41 compound microscope and subsequently combined in Helicon Focus software.Scanning electron micrographs of the holotypes of the new species were taken using Hitachi S-3700N environmental electron microscope at the Department of Paleontology, National Museum in Prague.General morphological terminology follows Hansen (1999) and Fikáček et al. (2009).
Prothorax.Pronotum evenly convex forming continuous curve with elytra in lateral view.Lateral margin weakly sinuate; with narrow marginal bead.Pronotal punctation uniform in size, moderately dense; slightly sparser than that on frons, consisting of small, rasp-like punctures, slightly sparser laterally than medially; all punctures bearing long setae; interstices without microsculpture.Transverse row of punctures on posterior margin of pronotum absent.Median portion of prosternum not elevated and demarcated from lateral portions, median carina of prosternum narrow, projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Postero-mesal projection with deep notch.Antennal groves moderately large.Lateral margin of antennal grooves rounded.
Etymology.The new species is dedicated to our friend Robert S. Anderson (Canadian Museum of Nature, Ottawa), a very enthusiastic entomologist and collector of the type specimens.
Distribution.Oosternum andersoni sp.n. is a Cuban endemic species currently known from the western, central and eastern parts of the island (Fig. 61).
Habitat.Most specimens were sifted from wet leaf litter in evergreen montane forests.
Coloration.Coloration of dorsal side of head, pronotum and elytra dark brown.Ventral side brown.
Prothorax.Pronotum evenly convex forming continuous curve with elytra in lateral view.Lateral margin of pronotum angulate, with narrow marginal bead.Pronotal punctation uniform in size, moderately dense, slightly denser than that on frons, consisting of small, rasp-like punctures similar on whole surface of pronotum; all punctures bearing long setae; interstices without microsculpture.Median portion of prosternum not elevated and demarcated from lateral portions, median carina of prosternum narrow, projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Postero-mesal projection with deep notch.Antennal groves moderately large.Lateral margin of antennal grooves rounded.
Etymology.The new species is dedicated to the Dominican radio station El Bacharenge, a source of the Caribbean music for the first author during his studies in the Czech Republic.
Distribution.Oosternum bacharenge sp.n. is a Hispaniolan endemic species currently only known from the type locality in the northeastern part of the Dominican Republic (Hato Mayor province) (Fig. 61).
Habitat.Based on the label data, the type specimens was collected in litter between tree buttresses in the rain forest.
Coloration.Coloration of dorsal side brown to dark brown, elytra darker than pronotum, head dark brown.Ventral side brown.Femora and tibiae brown, tarsi and mouthparts yellow.
Prothorax.Pronotum evenly convex forming continuous curve with elytra in lateral view.Lateral margin of pronotum angulate, with narrow marginal bead.Pronotal punctation uniform in size, moderately dense, as dense as that on frons, consisting of small rasplike punctures similar on whole surface of pronotum; all punctures bearing long setae; interstices without microsculpture.Median portion of prosternum not elevated and demarcated from lateral portions, median carina of prosternum narrow, not projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Postero-mesal projection with deep notch.Antennal grooves moderately large.Lateral margin of antennal grooves subangulate.
Metathorax.Metaventrite distinctly shorter than preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion consting of sparsely arranged but large rasp-like setiferious punctures, interstices without microsculpture, shiny.Anterolateral ridges bent posteriad along lateral margin of metaventrite, concave laterally, not meeting together mesally.Anterior margin of metaventrite not crenulate.
Etymology.The species name is derived from the name of the megasternine genus Cercyon Leach, 1817, reflecting the Cercyon-like appearance of this new species.
Distribution.Oosternum cercyonoides sp.n. is a Jamaican endemic currently only known from the type lo-cality in the Blue Mountains, i.e. the highest mountain massif in the eastern part of the island (Fig. 61).
Habitat.Based on the label data, the specimens were collected using baited pitfall traps in the montane cloud forest.
Prothorax.Pronotum evenly convex, slightly more convex than elytra in lateral view; lateral margin angulate, with narrow marginal bead.Pronotal punctation consisting of two types of punctures, large rounded without seta and smaller transverse with long seta; interstices without microsculpture.Transverse row of punctures on posterior margin of pronotum hardly defined.Median portion of prosternum elevated and demarcated from lateral portion.Median carina of prosternum narrow, projecting more anteriad mesally than anterior margin of median portion, straight in lateral view.Median portion of prosternum 1.2× wider than long, postero-mesal projection with shallow notch.Pair of deep pits next to ridge delimiting median portion of prosternum present.Antennal grooves moderately large.Lateral margin of antennal grooves with acute projection.
Metathorax.Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture reaching nearly to lateral margin; punctation of median portion sparse consisting of small, rounded punctures, interstices without microsculpture, shiny.Anterolateral ridges bent posteriad along lateral margin of metaventrite, angulate laterally, not meeting together mesally.Anterior margin of metaventrite crenulate.
Etymology.The species name is the manuscript name used in an unpublished revision of the genus Oosternum by M. Hansen -it was the only West Indian endemic in the manuscript, hence the highlighting of the fact that it is the island endemic.
Distribution.Oosternum insulare sp.n. is the Jamaican endemic currently known from three localities throughout the island, all situated in the altitudes around 500 m a.s.l.(Fig. 61).
Habitat.Specimens of O. insulare were collected from leaf litter of the well-preserved semi-deciduous forest in the karst area.Diagnosis.Body widest on base of elytra.Lateral margin of pronotum angulate.Pronotal punctation uniform in size, sparse, consisting of small, rasp-like, weakly impressed punctures.Pronotal interstices with microsculpture.Mesal part of prosternum divided from lateral portions by oblique sharp ridges.Lateral margin of antennal grooves with acute projection.Elytral interval 2 narrower than interval 3, lower than intervals 1 and 3, reaching elytral apex.Intervals 5, 7 and 9 distinctly higher than adjacent intervals.Elytral interstices opaque, with very fine microsculpture.Preepisternal plate wide, suboval, 2× longer than wide.Interstices of median part of metaventrite without microsculpture, with subpentagonal slightly elevate median portion.Anterolateral ridges of metaventrite not meeting together mesally.Parameres 1.2× longer than phallobase, bearing two short setae apically.Median lobe longer than parameres, projecting slightly farther than parameres, nearly parallel-sided basally, narrowing apicad in apical 0.2.Membranous lateral projections of median lobe present.
Distribution.Oosternum latum is the endemic of the Saint Vincent Island (Fig. 61).The specimens examined for this study represent the first precisely localized material available for the species, as only the island name is mentioned in the locality label of the type specimens (Fikáček et al. 2009).
Habitat.Specimens of O. latum examined here were collected in a lower montane rain forest with mixed forest plant compositions.A portion of the specimens were collected using flight intercept traps, and others using a Malaise trap.Diagnosis.Body widest ca at midlength.Lateral margin of pronotum weakly sinuate.Pronotal punctation uniform in size, moderately dense consisting of small, transverse punctures.Pronotal interstices with microsculpture.Mesal part of prosternum divided from lateral portions by oblique sharp ridges.Lateral margin of antennal grooves with acute projection.Elytral interval 2 narrower than interval 3, lower than intervals 1 and 3, reaching elytral apex.Elytral intervals 5, 7 and 9 distinctly higher than adjacent intervals.Elytral interstices shiny, without microsculpture.Preepisternal plate narrow, drop-like, 2.6× longer than wide.Interstices of median portion of metaventrite with strong mesh-like microsculpture on the whole surface.Anterolateral ridges of metaventrite not meeting together mesally.Parameres 1.2× longer than phallobase, bearing two short setae apically.Median lobe slightly longer than parameres, nearly parallel-sided basally, narrowing apicad in apical 0.4.Membranous lateral projections of median lobe present, with series of long setae on each side.
Coloration.Coloration of dorsal side of head, pronotum and elytra dark brown.Ventral side brown.
Prothorax.Pronotum forming continuous curve with elytra in lateral view; lateral margin weakly sinuate, with narrow marginal bead.Pronotal punctation uniform in size, moderately dense, as dense as that on frons consisting of small, transverse punctures similar on whole surface of pronotum; punctures with minute setae intermixed among those bearing long setae; interstices with microsculpture.Transverse row of punctures on posterior margin of pronotum absent.Median portion of prosterum elevated and demarcated from lateral portins; median carina of prosternum narrow, projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Median portion of prosternum 1.8× wider than long, postero-mesal projection with shallow notch.Pair of deep pits next to ridge delimiting median portion of prosternum present.Antennal grooves moderately large.Lateral margin of antennal grooves with acute projection.
Metathorax.Metaventrite ca. as long as preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion moderately dense, consisting of large, sharply impressed round setiferous punctures, interstices with strong mesh-like microsculpture on the whole surface.Anterolateral ridges bent posteriad along lateral margin of metaventrite, concave, laterally not meeting together mesally.Anterior margin of metaventrite not crenulate.
Etymology.The species name is derived from the woman's name Lucia, referring to the presence of this species in the Saint Lucia island.
Distribution.Oosternum luciae sp.n. is an endemic of Saint Lucia island and currently known only from the type locality (Fig. 61).
Habitat.Based on the label data, the type specimen was collected using an UV light trap.
Diagnosis.Body widest ca at midlength.Lateral margin of pronotum angulate.Punctation uniform in size, moderately dense, consisting of small, rasp-like punctures.Pronotal interstices without microsculpture.Mesal part of prosternum not divided from lateral portions.Lateral margin of antennal grooves rounded.Elytral interval 2 narrower than interval 3, as high as intervals 1 and 3, reaching elytral apex.Elytral intervals 5, 7 and 9 as convex as adjacent intervals.Elytral interstices shiny, without microsculpture.Preepisternal plate narrow, drop-like, 2.3× longer than wide.Interstices of median part of metaventrite without microsculpture.Anterolateral ridges of metaventrite not meeting together mesally.Parameres 0.8× longer than phallobase, bearing two long setae apically.Median lobe longer than parameres, oval in shape, with small apical projection.Membranous lateral projections of median lobe absent.
Coloration.Coloration of dorsal side brown to dark brown, head, pronotum and elytra dark brown.Ventral side light brown.Femora, tibiae, tarsi and antennomeres and light brown, antennal club dark brown.
Prothorax.Pronotum evenly convex forming continuous curve with elytra in lateral view.Lateral margin of pronotum angulate; with narrow marginal bead.Pronotal punctation uniform in size, moderately dense, as dense as that on frons; consisting of small rasplike punctures, slightly sparser laterally than medially; all punctures bearing long setae; interstices without microsculpture.Median portion of prosternum not elevated and demarcated from lateral portions, median carina of prosternum narrow, projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Postero-mesal projection with shallow notch.Antennal grooves moderately large.Lateral margin of antennal grooves rounded.
Metathorax.Metaventrite distinctly longer than preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion sparse consisting of small rounded punctures, interstices without microsculpture, shiny.Anterolateral ridges bent posteriad along lateral margin of metaventrite, concave laterally, not meeting together mesally.Anterior margin of metaventrite not crenulate.
Etymology.The new species is dedicated to our excellent colleague and friend Yoandri S. Megna (Universidad de Oriente, Santiago de Cuba, Cuba).
Distribution.Oosternum megnai sp.n. is the Cuban endemic species currently known only from the type locality in the southeastern part of the island (Granma province) (Fig. 61).The locality is situated in the Sierra Maestra mountain range which is considered one of the main centers of diversity in Cuba (CENAP 2004).
Habitat.Specimens of O. megnai were collected in dry leaf litter in the secondary forest.
Prothorax.Pronotum evenly convex, forming continuous curve with elytra in lateral view.Lateral margin of pronotum angulate, with narrow marginal bead.Pronotal punctation double-sized, dense, slightly denser than on frons, consisting of transverse punctures anteriorly and large round punctures posteriorly; all punctures bearing long setae; interstices without microsculpture.Median portion of prosternum not elevated and demarcated from lateral portions, median carina of prosternum narrow projecting more anteriad mesally than anterior margin of median portion, with anterior portion elevated into small tooth in lateral view.Postero-mesal projection with deep notch.Antenal grooves moderately large.Lateral margin of antennal grooves rounded.
Metathorax.Metaventrite distinctly shorter than preepisternal elevation of mesothorax, median portion markedly differing from lateral portion in punctation and microsculpture; punctation of median portion sparse, consisting of small rounded punctures, interstices without microsculpture, shiny.Anterolateral ridges bent posteriad along lateral margin of metaventrite, concave laterally, not meeting together mesally.Anterior margin of metaventrite not crenulate.Lateral margin with additional slightly concave ridge.
Etymology.The new species is dedicated to Professor Stuart Peck (Carleton University, Canada) whose collecting trips accumulated a huge material of the West Indian Hydrophilidae, including many Oosternum specimens used for this study.
Distribution.Oosternum pecki sp.n. is a Hispaniolan endemic species currently known only from the type locality situated in the southern part of the Dominican Republic (Barahona province) (Fig. 61).
Distribution.Oosternum sharpi is a common species distributed throughout the West Indies.We are recording it from all islands of the Greater Antilles (Cuba, Jamaica, Hispaniola and Puerto Rico) as well as from 9 islands of the Lesser Antilles.The species is otherwise widely distributed in southern USA, Central America and northern part of the South America, and was also introduced to the Azores (Orchymont 1940, Svensson 1973), Hawaiian islands (Hansen 1995), Ghana (Smetana 1978) and Sri Lanka (Hansen 1995).All specimens but one examined by us from the West Indian islands were females.The only male known from the West Indies is from Puerto Rico.
Habitat.Specimens of O. sharpi are often collected from dry leaf litter of secondary forests or other secondary types of vegetation (including bamboo stands in agricultural areas), and are also found in cow and horse dung in the lowlands or occasionally attracted to UV light.
Comment.The single examined specimen is very similar to O. sharpi but differs from it by the relatively smaller preepisternal plate of the mesothorax, central portion of the metaventrite with much finer punctation and the laterally incomplete anterolateral ridge (Fig. 48).However, since only a single female is available, we refrain from describing it as a new species, pending the discovery of additional specimens and ideally males.

Discussion
Composition of the West Indian fauna of Oosternum.Ten species groups of Oosternum were defined by Fikáček et al. (2009), using a set of arbitrarily selected characters (prosternal morphology, the form the pronotum, elytral morphology and the morphology of the metaventrite).These groups were aimed to divide the genus into smaller parts facilitating the species-level revision.Their phylogenetic significance has never been tested, yet they are the only available proxy of the internal structure of Oosternum at the moment.Moreover, additional characters exclusively correlating with some of the groups or their combinations were subsequently found (Fikáček 2009), which possibly indicates that at least some of these groups are candidates for monophyletic clades.
Representatives of five different species groups were found in the West Indies.Four species, the widely distributed O. sharpi, the endemic O. insulare and O. luciae, and the undescribed species from the Bahamas, are members of the O. sharpi species group (indicated by circles in Fig. 61).One species, O. latum, is a member of the O. aequinoctiale group (Fikáček et al. 2009; cross-shaped symbol in Fig. 61), which seems to be morphologically very close to the O. sharpi group based on the medially differentiated prosternum, pronotal punctation consisting of two intermixed types of punctures (one with long seta, one with extremely reduced seta) and antennal grooves with acute lateral projection.Further five species represent the groups without differentiated median portion of prosternum.They key out as members of Oosternum group C (in case of O. cercyonoides) and of the O. pubescens group (in case of O. andersoni, O. bacharenge, O. megnai and O. pecki) using the key to groups by Fikáček et al. (2009), as they differ in the morphology of the elytral intervals.However, the close relationship of the West Indian species with O. pubescens (LeConte, 1855) seems rather improbable, as the latter species is unique among Oosternum by possessing a partially differentiated median portion of prosternum (see Fig. 250 in Smetana 1978, under the name Cercyon pubescens).In contrast, all West Indian species bear a simply carinate prosternum.Moreover, O. pecki seems rather isolated from the remaining West Indian species based on its unique morphology of the meso-and metaventrite (preepisternal plate largely overlapping over metaventrite, metaventrite with an additional lateral ridge along the lateral margin) as well as by the character of the pronotal punctation (shape of the punctures changes from anterior margin to the posterior one).We therefore tentatively consider the West Indian species with simple prosternum as members of three species groups: O. cercyonoides and O. pecki each represent a separate species group (marked by a rhomboid and a triangle in Fig. 61, respectively), whereas O. andersoni, O. bacharenge and O. megnai are extremely similar to each other and form the group depicted by squares in Fig. 61.
Biogeography of the West Indian Oosternum.Nine of the ten Oosternum species occurring in the West Indies are thusfar endemic to the region.All of them are single-island endemics.The highest diversity is found in the Greater Antilles, where six endemic species were found, two on each island (Cuba, Jamaica, Hispaniola) except for Puerto Rico, from where no endemic species is known.In the Lesser Antilles, only two endemic species are known from the southern part of the island arc; one from each Saint Lucia and Saint Vincent islands.
Based on the assignment to the tentative species groups discussed above, the fauna of the Greater Antilles clearly shows a composite character, hosting representatives of five different species groups.Each Jamaican endemic species belongs to a different species group, and the same is the case of Hispaniola.This seems to indicate that the fauna of these islands resulted from multiple independent colonizations.A different situation is found in Cuba, where both endemic species, O. andersoni and O. megnai, are morphologically very similar and very likely closely related.They are moreover very similar to O. bacharenge from Hispaniola.It is hence probable that the three species are closely related.The geological block that today forms the northern part of Hispaniola was originally connected to that of eastern Cuba until the Early to Middle Miocene when it separated (Graham 2003).Hence, Oosternum bacharenge may have originated by vicariance after the separation of northern Hispaniola from Cuba.In Cuba, the two endemic species were never collected syntopically: Oosternum andersoni is a highland species widespread throughout the island, whereas O. megnai is endemic to the western part of the Sierra Maestra Mts.The type locality lies at the slope of Pico Turquino, i.e. the highest Cuban mountain.We failed to find the species in the central and eastern parts of Sierra Maestra despite our recent intensive collecting effort in these areas, which confirms that O. megnai is very likely a very local endemic.To understand the reasons for the within island split of O. andersoni and O. megnai, it would be necessary to date the age of the split.However, a local split along the elevation gradient seems currently as the most probable explanation.
Although data from other islands of the Greater Antilles are more limited than those from Cuba, the separation along the altitudinal gradient is likely also present in Jamaica, where O. cercyonoides is known from the highest mountain range only (Blue Mountains in eastern Jamaica, the type locality at 1600 m a.s.l.), whereas O. insulare is known from localities at around 500 m a.s.l.across the island.In this case, the species are however not related to each other, but the different environmental requirements may have facilitated their coexistence in the island after two independent colonizations.The composite character of the Hispaniolan fauna may on the other hand reflect the composite geological origin of the island.The current island consists of two originally separate blocks.The northern one was connected to eastern Cuba until the Early/Middle Miocene (as discussed above), whereas the southern one originally formed a separate island and was connected with the northern one in the Middle Miocene (Graham 2003).One Hispaniolan endemic species is known from the former northern island (O.bacharenge), the other from the former southern island (O.pecki) and they are moreover not closely related to each other.The probable origin of O. bacharenge was already discussed.Oosternum pecki may have originally been the sole endemic in the small island of Southern Hispaniola, resulting from the dispersal from the continent or another West Indian island.
The endemics of the Lesser Antilles are most probably not closely related, and are both known from the volcanic island in the south of the island arc (O.luciae from St. Lucia, O. latum from St. Vincent), i.e. those which are rather close to the South American continent.The taxonomy and distribution is known in detail at least for the O. aequinoctiale group to which O. latum belongs.All species of this group but O. latum are restricted to South and Central America, and none of them, including the otherwise very widespread O. aequinoctiale (Motschulsky, 1855), does not occur in the West Indies (Fikáček et al. 2009).It seems hence probable that O. latum colonized the volcanic island of St. Vincent from South America.Same may be true for O. luciae which also has its relative species only in South America (Fikáček, unpubl. data) and is not related to any other West Indian species.
Unbalanced sex ratio of West Indian populations of O. sharpi?Oosternum sharpi is the only species of the genus that is widespread in the West Indies and also the only one that is not endemic -it is also widespread in the continental Central and South America and in the southern USA (this material was not studied in detail in this study).Surprisingly, the vast majority of the West Indian specimens of this species examined by us (64 of 65 specimens) are females.No males were found in most islands, with the only exception of Puerto Rico, from which the only West Indian male of the species is known.Even through this may be accidental due to a small number of specimens collected in most collecting events, it still stands in contrast to most other West Indian Oosternum species treated here in which males were found despite the limited number of collected specimens.It is also in a strong contrast to the continental populations of O. sharpi, in which males are frequent (M.Fikáček, unpubl. data).Additional collecting is needed to test whether the absence of males in most islands is just a collecting bias, or whether some island population of O. sharpi may be parthenogenetic.The latter possibility would however correspond with the wide distribution of the species in the West Indies as well as with the fact that O. sharpi is the only species of the genus which was introduced outside of the Neotropical Region (as a single female is able to establish a new population in parthenogenetic species).

Figure 61 .
Figure 61.Distribution of the representatives of the Oosternum from West Indies.Shape of the symbols indicate the species group which the respective species belongs to (see the Discussion for details).