Series: Bulletin of the American Museum of Natural History (AMNH Bulletins) Volume: 410
362 pages, 233 colour & b/w photos and b/w line drawings, 32 b/w distribution maps
The spider genus Orchestina Simon is distributed worldwide and is characterized by having an enlarged fourth femur with which these species are capable of jumping. The genus is also characterized by having a well-sclerotized sperm duct, a near H-shaped arrangement of the eye group, a 4-4-3-3 pattern of raised receptors on the tarsal organs of the legs I-IV, respectively, and by lacking spines on all the legs. All these characters, together with molecular evidence, support the monophyly of the genus, as well as its placement as sister group of Oonopinae. Most American species of Orchestina inhabit the forest foliage and canopy, but in unforested areas they also occur in shrubs and grasses. In this work, we revise the American representatives of Orchestina in a comprehensive context for the first time.
In the past, six species were known from the Americas: five from the United States and only one from South America, described from Venezuela. After the study of the principal collections of the world and several field trips to several South American countries, we describe 85 new species and redescribe all previously known species. Matching sexes was occasionally problematic; while females are very homogeneous in somatic traits, males may have modifications on different parts of the body, making the matching very difficult. Therefore, in this review 56 of the species are described from only one sex, whereas 20 unmatched species are informally described as morphospecies, pending the discovery of conspecific sexes. Two species, O. pavesiiformis Saaristo and O. dentifera Simon, originally known from Israel and Sri Lanka, respectively, are here reported as introduced in several countries in the Americas and other continents. O. justini Saaristo described from the Seychelles is here considered a synonym of O. dentifera. One species, O. truncata Wunderlich, previously known as a subfossil spider from Colombian copal is here tentatively redescribed based on recent material from Costa Rica, Colombia, and Ecuador; the female is also described for the first time.
Although the internal relationships of the genus are still not clear, the authors suggest some groups of species based on morphological characters and geographic distributions. Species from the western United States share the presence of a net-shaped pattern of colouration and, in some species, modifications of carapace or first legs of males. Females of this group are characterized by the presence of a thin, generally long and twisted anterior receptaculum and external pockets on the epigastric region. This group inhabits in a geographic region that remained isolated during the late Cretaceous and is still isolated by geographic and climatic conditions. Species groups in South American members were more difficult to establish, given their wide diversity. However, some species are unique in having internal pockets in female genitalia and apophyses on the male copulatory bulb. The Chilean species are probably a monophyletic group; they are separated from the rest by the combined presence of external pockets and ridges on the epigastric region of female, whereas males are very similar in the morphology of copulatory bulb, which is very simple, with long embolus and sometimes with additional spine-shaped apophysis. This group may have experienced events of isolation during and after the elevation of the Andes range. As in other members of the family the genus is interesting for the presence of secondary sexual characters in males whereas females are practically homogenous in somatic characters. However, female genital morphology is variable, which may suggest a coevolution with somatic characters in males and probably mechanical interactions. Although this work reveals the incredible diversity of this genus, many important geographic regions remain undersampled and records for some countries are entirely lacking.
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