Halffterinetis violetae Morón & Nogueira, 2007

Ratcliffe, Brett, 2010, A review of the Blaesiina (Coleoptera, Scarabaeidae, Cetoniinae, Gymnetini), ZooKeys 34 (34), pp. 105-128 : 117-123

Halffterinetis violetae Morón & Nogueira, 2007

Figs 5, 11

Halffterinetis violetae Morón & Nogueira 2007: 56 .

Holotype male at CMNC and one paratype male at MXAL. Types labeled MEXICO: Durango, 40 mi SW Torreón, Hwy 40, 18-VI-1961, D. H. Janzen.

Description. Male (female unknown). Length 14.6–15.3 mm; width 7.9–8.4 mm. Color black, shining, lacking cretaceous marks. Head: Surface densely punctate to rugopunctate; punctures small to large, deep. Frontoclypeal region lacking transverse ridge. Frons with short, moderately dense, black setae. Clypeus with apex broadly truncate, strongly emarginate at middle, slightly reflexed, subapex distinctly wider than base, surface weakly concave. Interocular width equals 3.9 transverse eye diameters. Antenna black, with 10 segments, club almost twice as long as antennomeres 2–7. Pronotum: Surface densely punctate; punctures moder- ate to large, deep, round to slightly transverse, punctures becoming larger to rugopunctate on sides, and with short, tawny setae. Sides margined, bead reduced in anterior fifth. Mesepimeron completely punctate, with sparse, black setae. Elytra: Surface superficially and irregularly striate, rugopunctate, punctures moderate to large, round to mostly ∩-shaped, setigerous; setae short, sparse, black. Bead present on lateral margin. Apical umbone pronounced. Apices nearly right-angled. Pygidium: Surface with oval punctures or with short, transverse strigae (often reduced) to transversely strigose. Base usually with sparse, short, black setae. In lateral view surface weakly convex. Venter: Setae black. Mesometasternal process short, nearly obsolete, flat, apex rounded. Abdominal sternites with transverse, irregular field of large punctures; punctures sparser in central third, mostly large, shallow, with short, black setae. Legs: Femora and tibiae with sparse fringe of mostly short, black setae on median surface. Protibia tridentate, apical tooth longer, slightly narrower. Metafemur normal, not enlarged. Metatibia at apex with 2 broad lobes and with 2 long, articulated apical spurs with apices rounded. Metatrochanter triangular, elongate, flush with posterior margin of metafemur, acuminate apex not projecting perpendicularly. Parameres: Fig.11.

Distribution ( Fig. 5). Two specimens recorded from Morón and Nogueira (2007).

MEXICO (2): DURANGO (2): Torreón (40 mi SW on Hwy 40).

Temporal Distribution. June (2).

Biology. Morón & Nogueira (2007) indicated the habitat where this species was collected is semiarid with an average annual temperature of 12–18°C and located at 1287–1300 meters above sea level. Dominant plants consisted of Parthenium species ( Asteraceae ), Fouquieria species ( Fouquieriaceae ), Larrea species (Zygophiliacae), Hechtia species ( Bromeliaceae ), Opuntia species ( Cactaceae ), Agave species (Amarilidaceae), and Euphorbia species ( Euphorbiaceae ).

Biogeography

The distribution of blaesiine species ( Fig. 5) nearly mirrors that of Hologymnetis species, another genus within the Gymnetini . The biogeography of Hologymnetis species was reviewed by Ratcliffe and Deloya (1992) and is reviewed here to understand the similar distribution of the Blaesiina . Lacking fossil evidence for the Gymnetini , it is necessary to rely upon data from plate tectonics, present and paleodistribution of other plants and animals, and ecological factors to formulate a hypothesis to best explain the current distribution of these insects.

As with most other genera of New World Gymnetini , the ancestral Blaesiina were present in South America prior to the establishment of the Panamanian land bridge in the Miocene. Given the current distribution and ecological requirements of Blaesiina species, it is assumed that they evolved in drier habitats. Drier habitats have been present in South America since middle Tertiary time ( Webb 1978). The Quaternary (i.e., the last two million years) is characterized by great environmental instability ( Bigarella and Andrade-Lima 1982; Whitmore & Prance 1987). These climatic changes caused, in relatively short geologic time, successive expansions and contractions of either forest or open, drier vegetation. Forest and nonforest biomes broke up into isolated blocks or expanded and coalesced depending on varying humid or arid climatic conditions ( Haffer 1969, 1982; Vuilleumier 1971; Müller 1973; Prance 1973, 1982; Brown et al. 1974; Brown 1977; Tricart 1974; Simpson and Haffer 1978). With the reduction of forest vegetation during drier periods, there was a corresponding increase in nonforest formations that penetrated into the Amazon region from both north and south. Such formations consisted of large blocks or corridors connecting the open vegetation associations of the Central Brazilian Plateau with those of Venezuela and the Guianas ( Eden 1974; Sarmiento 1975; Bigarella and Andrade-Lima 1982; Marshall 1985).

Present day Blaesia species inhabit the mesic to semiarid, relatively open vegetation habitats of Bolivia, Paraguay, Uruguay, Argentina, and southern Brazil. The broad, continuous band of present-day Amazonian rainforest is a barrier preventing further dispersal northward. Ancestral Blaesiina would have been afforded suitable avenues for traversing previously inhospitable lowland forested regions in Amazonia by the extensions of savanna-like habitat (Fig. 12). With the establishment or re-establishment of rain forest in the Amazon basin, populations of ancestral Blaesiina became divided and isolated both to the north and south of the Amazon region. The northern lineage (today’s Halffterinetis species) ultimately dispersed to nuclear northern Mexico, and the southern lineage (today’s Blaesia species) became isolated in the woodland savannas south of the Amazon basin. As habitats changed through time, ancestral Blaesiina disappeared entirely from between northern Mexico and southern South America.

Pre-Miocene dispersal of the biota between North and South America was probably rare, and a small amount of biotic interchange agrees with the geologic evidence suggesting a relatively wide separation of the Americas in Cretaceous through Oligocene times ( Raven and Axelrod 1974; Smith and Briden 1977; Gose et al. 1980). Consideration of climate is important both before and after establishment of a land connection ( Stehli and Webb 1985b). For example, the existence of clear evidence of mountain glaciation along the continental divide in Guatemala suggests that simply extending present-day conditions back in time will not suffice to allow a real understanding of the physical nature of the link between the two Americas or of its effect on biotic interchange. After Mesoamerica coalesced during the Pliocene 3.0 MYBP ( Marshall 1988) to 5.7 MYBP ( Lloyd 1963; Kaneps 1979), an extensive faunal exchange began ( Webb 1978; Stehli & Webb 1985a). Formation of the Panamanian isthmus dispersal route permitted separate invasions of plants and animals at widely separated periods when climates and topographic features were different than today.

After the formation of the isthmus of Panama, members of the Gymnetini began their northward dispersal from South America into Central America, Mexico, and the United States. Webb (1978, 1985) provided an excellent analysis of the interamerican biotic exchange, pertinent parts of which are described here. The interval from 2.5– 1.5 MYBP shows an extensive movement of savanna-adapted mammal faunas from south temperate to north temperate latitudes and vice versa. All of the animals that

Figure ļ2. Maps showing approximate distribution of savannas (gray areas) in South America at a about 4.0 MYBP, b during glacial maxima, and c today. Arrow in b shows most likely dispersal route of taxa living in savanna habitats (after Marshall 1985).

are known to have dispersed between the Americas in the late Tertiary were tolerant of, or specifically adapted to, savanna woodland habitats. The savanna elements were not incidental parts of the interchange but represent the vast majority of the taxa involved. Notable among them were horses, llamas, armadillos, and ground sloths. The extent of savanna adaptations among the land mammals of the interchange indicates the presence of a uniformly nonforested corridor or a moving mosaic of such habitats between South America and North America. The more arid conditions that must be postulated for the isthmian region during its early history probably supported seasonal forests grading into thorn scrub savannas. Similar habitats exist today in northern Venezuela and eastern Colombia and on the Pacific slopes of Central America from western Panama northward. Less mesic conditions in the isthmian corridor were a result of a combination of factors having to do with climatic fluctuations associated with northern hemisphere glaciations, lowering of sea levels (with a concomitant increase in land area), regional uplift with large-scale volcanic extrusion, and creation of rain shadow regions.

The glacial maxima at and following the emergence of the Panamanian land bridge, combined with the presence of a north-south corridor over the bridge, occurred only twice in the late Tertiary ( Shackelton and Opdyke 1977; Cronin 1981). These times (2.5 and 1.8 MYBP) represent “optimal ecological windows” that permitted dispersal of taxa living in savanna habitats between the Americas ( Marshall 1985). The earliest known South American mammals to disperse to North America across the Panamanian land bridge occur in rocks dated at 2.8–2.6 MYBP. This reciprocal event favoring savanna-adapted forms could not have occurred earlier due to absence of a suitable corridor, habitat, and climate. Subsequent opportunities did not exist until the next glacial maxima at about 2.0–1.9 MYBP ( Marshall 1985). “Thus, two synchro- nous and reciprocal dispersal events of late Tertiary age are recognized. The first event (2.8–2.6 Ma) included dispersal of Erethizon Cuvier , Neochoerus Hay , Glyptotherium Osborn, Glossothrium Glossothrium Owen, Othrotheriops Hoffstetter , Kraglievichia Casatellanos , and Dasypus L. (and the ground bird Titanis Brodkorb ) to North America, and Conepatus Gray , Hippidion Roth , and Platygonus LeConte to South America. The second event (2.0–1.9 Ma) included dispersal of Hydrochoerus Brisson , Eremotherium Spillmann , and Holmesina Simpson to North America, and Arctodus Leidy , Galictis Bell , Felis L., Smilodon Lund , Tapirus Brünnich , Hemiauchenia Gervais and Ameghino , Onohippidium Moreno , and Cuvieronius Osborn (and possibly Stipanicicia Reig , Dusicyon Smith , and Protocyon Giebel ) to South America. Only one dispersal event of early Pleistocene age is evident, and this occurred at about 1.4 Ma. It corresponds to the earliest of the Pleistocene glacial maxima recognized by Cronin (1981) and follows the one at 2.0–1.9 Ma. During this event, Canis L., Lutra Brisson , Chrysocyon Hamilton- Smith, Cerdocyon Hamilton-Smith, Leo (=Panthera Oken), and Stegomastodon Pohlig dispersed to South America, and Didelphis L. and Palaeolama Gervais dispersed to North America” ( Marshall 1985). The last glacial maximum permitting dispersal of savanna biotas over the land bridge occurred 12,000 –1,000 years B.P. ( Bradbury 1982; Markgraf and Bradbury 1982). A savanna corridor formed along the eastern side of the Andes connecting the now disjunct habitats in South America (Fig. 12).

The major obstacles to such dispersal events were distance and potential competitive exclusion. Given that cetoniines are capable of such powerful flight, distance may not have been such a deterrent to long distance dispersal. The Japanese beetle ( Popillia japonica Newman ) ( Scarabaeidae : Rutelinae ), for example, has spread from the east coast of North America (where it was introduced) to the central states (1,900 km away) in only 70 years; that averages 27 km /year. Aphodius fimetarius (L.) ( Scarabaeidae : Aphodiinae ), introduced into North America from Europe probably in colonial times, is now found over much of the continent. Digitonthophagus gazella (Fabr.) has dispersed from 43 to 808 (!) km/year in Mexico and the U.S. (Barbero and López- Guerrero 1992). The tussock moth, monarch butterfly, European corn borer, and honeybee all represent contemporary examples of long distance dispersal by insects in short periods of time. The Africanized honeybee, Apis mellifera scutellata Lepeletier , has dispersed 300–500 km per year from southern Brazil to northern Mexico in only 30 years ( Camazine & Morse 1988). The rapid and historically near-instantaneous colonization of the Australian continent by the European hare, Lepus europaeus Pallas , highlights the phenomenal dispersal ability of a small mammal ( Marshall 1985). The opossum, Didelphis marsupialis L., had an average dispersal rate of 50 km /year during the 26 years following its introduction into California ( Tyndale-Biscoe 1973). At such a rate this species could extend its range 25,000 km in only 500 years ( Savage and Russell 1983). Martin (1973) noted that a conservative dispersal rate of 16 km / year would have permitted prehistoric humans to spread from Canada to Tierra del Fuego in less than 1,000 years. The dispersal of insects between the mid-continental regions of North and South America may have occurred in only a few thousand years with the availability of suitable habitat. The vertebrate fossil evidence clearly indicates that dispersal of savanna-adapted animals occurred twice in the late Tertiary. South American ancestral Blaesiina , adapted to dry habitats, was part of that dispersal. Webb (1978) observed that it may be difficult for some biologists to accept so short a time scale for such evolutionary change, but the paleontological record of the interamerican interchange demonstrates that two or three million years is sufficient time to produce fundamental evolutionary reorganization of a major biota.

The late Pleistocene shift to more humid conditions in lower Central America produced a major set of savanna disjunctions spanning the isthmian gap ( Webb 1978). The disjunct distribution across the American tropics shared by many presentday organisms provides additional evidence of a previous woodland savanna corridor. Within the temperate to subtropical Areodina ( Scarabaeidae : Rutelinae ), six genera are found ranging from the United States to Guatemala, and three genera are found in South America ( Jameson 1990). None of these genera occur in the remainder of Central America, which, for the most part, has been historically covered by tropical rainforest. This Central American gap might seem like a paradox until, noticing its occurrence in other groups, we recognize a pattern. Many birds adapted to savanna or thorn scrub show a wide interamerican disjunction. These include the Green Jay, Military Macaw, Melodious Blackbird, Homed Lark, Vermillion Flycatcher, small woodpeckers, and the Grasshopper Sparrow ( Griscom 1950; Mengel 1970). Cricetid rodents such as Reithrodontomys Giglioli skip from semiarid habitats in Nicaragua to similar habitats in the Andes, and Crotalus L. vipers (preferring scrub habitats) now have a large gap across the rainforest of the isthmus ( Webb 1985). The distributional gap across the isthmian region is well known for many plants as well as many bees that specialize on these plants ( Raven 1963; Solbrig 1972; Rzedowski 1973; Simpson and Neff 1985). Webb (1985) observed that one of the most convincing indications of former continuity is a string of relict populations of Larrea Cav. in Peru and Bolivia partly connecting its main south temperate and north temperate ranges. This idea is strengthened by the fact that one of the principal foods of the extinct ground sloth ( Nothrotheriops Hoffstetter species), as indicated by its dung, was Larrea , and that both genera clearly came to North America from temperate South America ( Martin et al. 1961; Hunziker et al. 1973). By the late Pleistocene, as now, woodland savanna taxa were excluded from the isthmian region due to the dissolution of savanna habitats and replacement by tropical rainforest. Late Pleistocene pollen samples from Lake Gatun in Panama reveal a forest flora much like that of present lowland Panama ( Webb 1978). About 1,700 km of tropical wet forest extending from Costa Rica and Panama through northern Colombia now separates the nearest areas of savanna and thorn forest ( Sarmiento 1976). Consequently, ancestral Blaesiina were also excluded from this region because they could not survive in tropical wet forests. Northern Central America retained a woodland savanna fauna as evidenced by the present biota and Pleistocene samples from Guatemala, Honduras and El Salvador ( Stirton and Gealey 1949; Carr 1950; Duellman 1966; Savage 1966; Woodburne 1969; Howell 1969). Species of Halffterinetis are today found in mesic to xeric habitats in north central Mexico.

Based on his analysis of the entomofauna, Halffter (1976) formulated several different dispersal patterns to explain the present distribution of taxa in the Mexican Transition Zone. The distribution of Halffterinetis species coincides well with Halffter’s “Typical Neotropical Dispersal Pattern”. In this pattern, South American elements penetrated into the Mexican Transition Zone after the formation of the Panamanian land bridge and after most of the elevation of the Mexican Plateau. As ancestral Blaesiina spread northward, they used as their principal expansion route from Central America the mountains of Oaxaca and the Sierra Madres, which funneled the dispersal of Blaesiina to the west and north, respectively, where Halffterinetis species occur today.

Acknowledgments

I am grateful to the institutions, curators, and collection managers mentioned in the “Methods” section for their generous cooperation in either loaning or allowing me access to specimens under their care. I thank Mary Liz Jameson (then University of Nebraska State Museum) for her assistance in collating specimen data at the National Museum of Natural History (Naturalis) in Leiden. I am grateful to two anonymous reviewers for their constructive criticism of the manuscript. Miguel Morón (Instituto de Ecología, Xalapa, Mexico) is gratefully acknowledged for permission to use Figures 6–9, which originally appeared in his 2007 paper on Halffterinetis . I thank Angie Fox (Scientific Illustrator, University of Nebraska State Museum) for making ready the figures, maps, and image files. This project was supported by an NSF/BS&I grant (DEB 0716899) to B. C. Ratcliffe and R. D. Cave and an NSF Multiuser Equipment grant (DBI 0500767) to M. L. Jameson and F. Ocampo.