The Genus Diaprepes
Its Origin and Geographical Distribution in the Caribbean Region
Charles W. O'Brien and Peter W. Kovarik
Center for Biological Control
Florida A&M University
Tallahassee, FL 32307-4100 USA
Abstract
The weevil genus Diaprepes Schoenherr is restricted to the Caribbean region with 15 species from the West Indies and one from Trinidad, Tobago and Venezuela. Diaprepes abbreviatus (Linnaeus) was introduced into Florida in 1964 and since then has become a serious pest of citrus there. The relationship between Diaprepes and Exophthalmus Schoenherr is discussed, and both genera are diagnosed. The difficulties in identifying species and distinguishing species from their numerous morphs are described. Two Central American species are moved from Diaprepes to the genus Exophthalmus: E. albofasciatus (Champion) [NEW COMBINATION] and E. pulverulentus (Champion) [NEW COMBINATION]. A checklist is included for the 16 valid species of Diaprepes. This list includes information on distribution and synonymy. Several species of Diaprepes including abbreviatus (L.), abbreviatus "adjuntas" morph, famelicus (Olivier), marginatus (Fabricius) maugei (Boheman), and rohrii (Fabricius) are illustrated in color.
The beetle family Curculionidae, commonly referred to as the weevils, represents the largest family of living organisms known, with more than 65,000 species described. A relatively conservative estimate of species in this group of insects puts the probable number of valid species at 250,000. Approximately 20% (14,000 species) belong to the group of weevils known as the "broad-nosed weevils" which include the small, but economically important genus Diaprepes Schoenherr (O'Brien and Wibmer, 1978). The focus of this paper is the origin and distribution in the Caribbean of the genus Diaprepes (Linnaeus). Also discussed in detail is the current uncertain status of the taxonomy of the species of Diaprepes and the closely related genera of citrus root weevils. This genus had 19 valid species, three subspecies, three varieties, and 17 synonyms (O'Brien and Wibmer, 1982; Wibmer and O'Brien, 1986). Two species of Central American Diaprepes are transferred here to the genus Exophthalmus Schoenherr, namely E. albofasciatus (Champion) [NEW COMBINATION] from Honduras, and E. pulverulentus (Champion) [NEW COMBINATION] from Nicaragua. One species, D. spengleri (L.), was synonymized by Marshall (1916) with D. abbreviatus (L.) and this synonymy has been overlooked by subsequent workers. Hence, the current number of valid species in Diaprepes is 16.
The first species of this genus was described in 1758 by Linnaeus in the genus Curculio, in which, in addition to the genus Attelabus,he placed all weevils known at that time. Later this species was placed in Diaprepes, and it happens to be the species of greatest economic importance, i.e. D. abbreviatus (Figs. 1, 2)(1). Diaprepes was first used in a list of genera by Schoenherr in 1823, who described the genus in 1826. Diaprepes abbreviatus was listed from the "Indiis" by Linnaeus without reference to the West Indies or East Indies. The original type specimen of D. abbreviatus is still in the museum in Lund, Sweden, where it was deposited more than two centuries ago.
The importance of archival collections of early taxonomists cannot be overstated. While some early descriptions are quite good, e.g. those of Schoenherr and his disciples (Boheman, Fahraeus, Gyllenhal, and Rosenschoeld), even these descriptions present problems by commonly making comparisons with known European species. For those not completely familiar with the European weevils, this can be problematic. Descriptions by many others very often are very short and general in the characters used. The descriptions of Linnaeus and Fabricius, the two earliest taxonomists, were extremely brief (a very few words or characters), and generally are useless to identify their species. This, plus the nearly universal lack of illustrations, make identifications from descriptions not merely difficult but nearly impossible. Even when illustrations are included (primarily in Atlases), the quality of the figures is very uneven, ranging from the occasional excellent habitus drawing (rarely handpainted in color) to the more frequent, poor line drawing, commonly drawn out of proportion and looking little like the species in question. In their defense, these workers had no idea that there were millions of species to be described, nor how many nearly identical, closely related species there were to be described.
Very often the only hope that a taxonomist has to positively identify a poorly described species is to study the type, perhaps dissect it, and compare it with other material. Most of the type material from the earliest periods of taxonomic study, i.e. 1758-1850, is found in European museums. Such material was gathered by early collectors (e.g. Charles Darwin) who traveled the world by ship, as biologist naturalists, or frequently as ships' doctors with an interest in natural history, and deposited their collections with friends or in museums. These natural history museums have preserved the specimens safely, and quite often in perfect condition. Since all but two species of Diaprepes were inadequately described by early taxonomists, it is essential that the senior author (CWOB) see the majority of these types. Until then it will be impossible to associate the correct names of many of the forms and species of Diaprepes and their close relatives.
Some broad-nosed weevils including Diaprepes and Exophthalmus can be extremely plastic in their external morphology. In Diaprepes, this plasticity is manifested in the presence of distinctive morphological forms (morphs) which occur in two different species, D. abbreviatus and D. famelicus (Olivier) (Figs. 5, 6). In Puerto Rico, there are seven to nine distinctive morphs, some widespread through the island and others endemic (known only from a single small geographic area). Several of these morphs have received formal subspecific names, some are known informally as varieties, while others still are informally designated by the locality where they have been collected, e.g. "adjuntas" (Figs. 11, 12). Four morphs, recognized as D. abbreviatus, while morphologically distinctive, have identical male genitalia, and clearly represent a single species. Unfortunately differences between several of the species recognized as valid are less distinctive and obvious than those seen in several of the morphs recognized to be the same species. However, in seven species dissected by CWOB, the male genitalia were examined, (i.e., abbreviatus, doublierii, excavatus, famelicus, marginatus (Figs. 9, 10), maugei (Figs. 7, 8), and rohrii (Figs. 3, 4), and the specific differences are evident in these genitalia, and although the external morphological differences are subtle, they are consistent and validate the species.
A careful study of approximately 1,000 specimens of D. abbreviatus collected in Puerto Rico has made it clear that the Florida populations of this weevil, were originally introduced from Puerto Rico. Populations from three localities near San Jose are identical to the Florida morph. These are from Carraízo Alto in the hills 3 km. S. of San Juan; Dorado, near the north coast, 16 km. W. of San Juan; and Fortuna, on the north coast, approximately 27 km. E. of San Juan. This discovery can be of great importance, because it will allow researchers to concentrate their searches for potential biological control agents in select areas in Puerto Rico.
In addition to study of the type material, crossing experiments, larval studies, and DNA analysis will enable us to properly define the species and produce a key that will allow others to identify the species as well.
The identification of the species is not the only problem that the taxonomist faces in this difficult group of weevils. The placement of species in the proper genus can be difficult. The frequent transfer of species among genera and the uncertain validity of various genera demonstrate the need for a comprehensive phylogenetic study of this group. Several workers (e.g. Kuschel, 1955; Marshall, 1916; Pierce, 1915; and Vaurie, 1961) have expressed doubt concerning the validity of the generic placement of numerous species in both Diaprepes and Exophthalmus, and some have suggested merging these two genera into a single, large, diverse genus. Kuschel (1955) stated that: "It is unquestionable that Diaprepes, Exophthalmus, Rhinospathe, and Callizonus [now Tropirhinus] on the one hand and Pachnaeus, Naupactopsis, Chauliopleurus, Decasticha, Tetrabothynus, Lachnopus, Ischionoplus, and Apotomoderes on the other, form one systematic entity, nevertheless, they can be distributed in two different subfamilies." It appears that these two groups of genera form two closely related clades, but determination of the validity of the genera awaits further study. Examples of all of these genera are in the collection of the senior author (CWOB). Vaurie (1961) has reviewed the taxonomic history of the genera Exophthalmus, Diaprepes, and Prepodes (a synonym of Exophthalmus, originally described as a subgenus of Diaprepes). Her discussion points out that there have been no revisions of the genera as a whole, making the identification of the species a very difficult task. A diagnosis will assist in the recognition of Diaprepes Schoenherr in spite of the fact that several of the critical characters are subjective, and a few are variable among the species currently placed in the genus. Because of the close relationship with Exophthalmus and the likelihood of confusing these two genera, emphasis is placed on their differences and a few of their similarities. Both genera are medium-sized to large (6.0-22.0 mm.); broad-nosed; often brightly colored (color usually associated with setae or scales); the antennal scrobes are lateral and evenly descending to the base of the eyes; the body is winged; the elytra possess supplementary striae (two or more abbreviated rows of punctures on the outer part of the elytral disk); the front tibiae are uncinate with a short to long, stout to slender hook; and usually all tibiae are denticulate. Diaprepes usually has well-developed postocular vibrissae (long setae used to keep the eyes clean); the eyes are elongate-oval, and only moderately convex (flatter, not strongly bulging). The rostrum is usually carinate (unicarinate to tricarinate) or longitudinally rugose. The second funicular segment is elongate, usually at least twice as long as the first, and the third segment is elongate, as well. However, Exophthalmus always lacks postocular vibrissae; the eyes are round to oval, and strongly convex (usually bulging). The rostrum usually is not carinate, although it often has a smooth median line, and occasionally has the margins ridged. The second funicular segment is usually subequal in length to the first, and the third is rarely elongate.
All currently known species of Diaprepes are native to the West Indies, except for D. comma, which is known only from Venezuela, Trinidad and Tobago. Of the remaining 15 valid species, five are known from the Greater Antilles, eight from the Lesser Antilles, one without specific locality from the "West Indies" only, and D. abbreviatus is currently known from both the Greater and Lesser Antilles (see checklist below). It is highly probable that man has moved D. abbreviatus among the islands, just as occurred in Florida in 1964 (Woodruff, 1964).
Checklist of Species of Diaprepes
Subspecies, Variations and Synonym, and Known Distributions
Synonyms and invalid names are indented and italicized.
[Based on previously published checklists (O'Brien and Wibmer, 1982; Wibmer and O'Brien, 1986) and new information gathered by CWOB]
Diaprepes Schoenherr 1823-column 1140 [1826-116] [Official Name 1959 - Opinion 572]
Key: Pierce 1915; Hustache 1929
abbreviatus (Linnaeus) 1758-386 (Curculio) FL (introduced); Barbados, Dominica, Guadeloupe, Hispaniola, Martinique, Mona, Montserrat, P. Rico, St. Lucia, St. Vincent, Vieques
- festivus (Fabricius) 1792-476 (Curculio)
- irregularis (Panzer) 1798-67 (Curculio) [also incorrectly attributed to Voet]
- japonensis (Voet) 1806-52 (Curculeones)
- spengleri (Linnaeus) 1767-609 (Curculio) [Synonymized by Marshall, 1916, overlooked by subsequent workers] P. Rico
- sommeri: Guenther & Zumpt 1933-109 [error, in part (all references earlier than 1840, and some later ones); P. E. Persson, pers. comm.]
- sprengleri [also sprenglerii]: (Linnaeus) 1767-609 (Curculio) [incorrect original spelling, emended Fabricius 1775-151]
v. brevis (Olivier) 1790-549 (Curculio) Guadeloupe, Martinique
- quadrilineatus (Olivier) 1807-310 (Curculio)
v. distinguendus Gyllenhal 1834-10 Guadeloupe, Martinique, P. Rico
- festivus (Olivier) 1807-312 (Curculio) [not Fabricius 1792]
- vicinus: Dejean 1834-252 & 1837-275 [nomen nudum]
v. guadeloupensis Gyllenhal 1834-11 Guadeloupe
- guadelupensis Hustache 1929-184 [not guadeloupensis Gyllenhal 1834]
balloui Marshall 1916-449 Dominica
boxi Marshall 1938-3 St. Lucia
comma Boheman 1834-8 ... [Dom. Rep., P. Rico (Chevrolat 1876-CCXXVII), misident. of doublierii Guérin 1847-9 (Marshall 1916-453)] Tobago, Trinidad, Venezuela
doublierii Guérin 1847-9 Dom. Rep., Haiti, P. Rico
- comma: Pierce 1915-258 [misidentification, not Boheman 1834]
excavatus Rosenschoeld 1840-343 St. Vincent
famelicus (Olivier) 1790-544 (Curculio) Dominica, Guadeloupe, Martinique, Nevis
- affinis (Fabricius) 1801-531 (Curculio)
- lepidopterus Gyllenhal 1834-14
- leucopterus: (Leng & Mutchler) 1914-469 (Exophthalmus) [error]
s. barbadensis Marshall 1916-451 Barbados
s. elegantulus Gyllenhal 1834-13 [also incorrectly attributed to Leng & Mutchler 1914-469] Cuba, Martinique
s. esuriens Gyllenhal 1834-15 Antigua, Montserrat, St. Barthélemy, St. Kitts
- purvesi Roelofs 1875-XXVI
glaucus (Olivier) 1807-315 (Curculio) W. Indies
marginatus (Fabricius) 1775-145 (Curculio) [Resurrected Name; incorrectly attributed to Olivier 1790-526] Guadeloupe
- bivittatus (Fabricius) 1787-118 (Curculio)
- circumdatus: Schoenherr 1826-117 [nomen nudum]
- denudatus Pierce 1915-263
maugei (Boheman) 1840-369 (Eustales) P. Rico
- capsicalis Marshall 1922-59
reticulatus Chevrolat 1880-165 Martinique
revestitus Chevrolat 1880-165 Cuba
rohrii (Fabricius) 1775-151 (Curculio) St. Croix
- farinosus Gyllenhal 1840-344
- lundii (Herbst) 1795-134 (Curculio)
- marginatus: Pierce 1915-258 [misidentification, not Fabricius 1775]
rufescens Boheman 1840-346 Guadeloupe
sommeri (Rosenschoeld) 1840-339 (Exophthalmus) [incorrectly attributed to Linnaeus 1767-609] Cuba
variegatus Chevrolat 1880-165 Martinique
Acknowledgments
We wish to thank Dr. Steve Lapointe, USDA-ARS for assistance in rearing Diaprepes and for specimens collected by him in Puerto Rico and by his colleague Miguel Serrano for specimens collected in St. Croix. Our special thanks to Dra. Rosa Franqui, University of Puerto Rico, for specimens collected, for important logistical support during our field trip to Puerto Rico, and for assistance in obtaining critical literature for our research. Our gratitude is extended as well to Drs. Lois B. O'Brien, FAMU and Stuart Reitz, USDA-ARS for critical reading of this manuscript. This research was supported in part by a grant, FLAX 97007 from CSREES (Cooperative State Research, Education, and Extension Service, USDA) for the senior author (CWOB) and a USDA-NBCI Post-Doctoral fellowship for the junior author (PWK).
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