Acmaeodera (Squamodera)

Davidson, J. M., 2003, Mexican Acmaeodera Eschscholtz, 1829: A new species and checklist, with miscellaneous taxonomic and biological notes on other North American Buprestidae (Coleoptera), Zootaxa 201, pp. 1-18 : 5-12

publication ID	https://doi.org/ 10.5281/zenodo.156682
DOI	https://doi.org/10.5281/zenodo.5690958
persistent identifier	https://treatment.plazi.org/id/03F43F6C-FFE5-7F30-FE83-F9628F0975AB
treatment provided by	Plazi
scientific name	Acmaeodera (Squamodera)
status

Treatment

Acmaeodera (Squamodera) View in CoL View at ENA , stat. nov.

Squamodera Nelson, 1996:167 .

Type species: Acmaeodera vanduzzei Van Dyke, 1934 (original designation).

Nelson (1996) described the genus Squamodera to accommodate four previously described species of A cmaeodera: A. barri Cazier, 1940 , A. constricticollis Knull, 1937 , A. ephedrae Barr, 1943 and A. vanduzzei Van Dyke, 1934 and its three synonyms (see below). The decision to erect a new genus for these species appears to have been based mainly upon anatomical characteristics which are sometimes found in other species of Acmaeodera as well as in related genera. The squamose setae or scales common to all species of Squamodera are also found on Acmaeodera mimicata Knull, 1938 , A. fattigi Knull, 1953 and A. lauta Barr, 1972 , as well as a few other species of Acmaeodera and related genera such as Acmaeoderopsis Barr, 1974 and Acmaeoderoides Van Dyke, 1942 . The latter genus is placed into a separate subtribe from the other genera discussed herein. The s errate parts of the antennae are indeed somewhat subcylindrical in Squamodera , but this feature is not unique to this small complex of species. The combination of characteristics used to define Squamodera is not sufficient to justify a genus separate from Acmaeodera .

Therefore, I propose Squamodera , and the four species and synonyms contained therein, be transferred to Acmaeodera as a subgenus (listed below). Unlike the Palearctic and Afrotropical Acmaeodera faunas, which have been well studied and divided into several subgenera (e.g. Volkovitsh, 1979, Holm, 1978, Holm & Schoeman, 1999), no comprehensive study of Nearctic or Neotropical A cmaeodera has been conducted with the objective of determining whether closely related species or species complexes should be placed in separate subgenera. Except for the four species in the subgenus Acmaeodera (Squamodera) , no Acmaeodera species known from the Nearctic or Neotropics have yet been placed into particular subgenera. Bellamy (1995) succinctly illustrated the very difficult task facing researchers who are working on the huge genus Agrilus Curtis, 1815 , in trying to divide this group into more manageable segments, i.e. subgenera. In his closing arguments, he suggested that we need to agree upon a "… philosophy that will allow researchers from different regions and backgrounds to approach their studies of Agrilus from some point of agreement, despite the fact that no clear definition or agreement has ever been reached about what constitutes a genus as opposed to a subgenus or species group." However, Holm & Schoeman (1999) presented "criteria and considerations on erecting genera" [and subgenera], and my approach here appears to coincide with their criteria for purposes of placing Squamodera as a subgenus of Acmaeodera . The fundamental principles espoused by both Bellamy (1995) and Holm & Schoeman (1999) apply not only to Agrilus , but also to Acmaeodera , Anthaxia Eschscholtz, 1829 , Chrysobothris Eschscholtz, 1829 , and other genera containing large numbers of species.

It appears that the four valid species included in Acmaeodera (Squamodera) might comprise a monophyletic group, i.e., are more closely related to one another than to any other species or species group, and are adapted to the hot dry deserts of the southwestern United States and adjacent northern Mexico. These species are very closely related and occasionally are difficult to separate from one another, especially A. (Squamodera) vanduzzei from A. (Squamodera) ephedrae . The latter species appears to be restricted to a relatively small sandy area in southern California. The former species occupies a considerably larger distributional range, at least as far north as the lower end of the Owens Valley and is sometimes found in environments with somewhat reduced amounts of sand. It seems to be most frequently associated with plants of the genus Eriogonum (Polygonaceae) . Acmaeodera (Squamodera) barri appears to have adapted to the southwestern deserts and occurs mainly on smokebush or smoketree, Dalea spinosa Gray (Fabaceae) , but sometimes utilizes other species of Dalea as well. This is a rather whitish or pale, smoky colored plant, and because A. (S.) barri is completely covered in silverywhite scales, may have found protection from predators by using this as an adult host or perch. Knull (1950) recorded Dalea as a larval host, and small oval emergence holes in Dalea spinosa I observed while collecting this species might indicate that A. (S.) barri uses this plant as a larval host as well. Acmaeodera (Squamodera) barri is found in western Arizona as well as in southern California. Acmaeodera (Squamodera) constricticollis appears to occupy a more restricted distribution in southeastern California, and appears to be allopatric with A. (S.) ephedrae , but partially sympatric with A. (S.) barri and A. (S.) vanduzzei . It occurs in areas where flowering arrow weed, Pluchea sericia (Nutt.) Coville (Asteraceae) is found, and it is evident this is at least one of its adult host plants. Thus, species of Acmaeodera (Squamodera) have radiated not only in differences in form and scale structure, but also to different geographic areas and adult (and perhaps larval) hosts, insuring that they do not compete with one another for resources.

In the recent past, approximately 5,000 to 10,000 years ago, the area in which these species are now found was much wetter than it is today, and the host plants that occur today did not exist at that time ( Betancourt, et. al, 1990). Many desert shrubs and small trees that exist in the southwestern deserts today originated much further south and invaded northward as temperatures warmed and the land became more arid. Whether these beetles are recently derived from a species or species complex from that period and adapted to gradual climatic and changes in plants, or whether these are merely invaders from Mexico cannot be determined with certainty. A similar situation is known from extreme southern Europe and North Africa, where the climate was more mesic over the same time period. Where the Sahara Desert now exists, a savanna with trees, shrubs and grasses occurred. Species of Buprestidae extant in North Africa are adapted to a much more xerophytic environment than in the previous ten millennia. Species of Acmaeodera (Squamodera) are slightly elongate, with white scales on various or all body parts. However, as previously mentioned, scales are not unique to A. ( Squamodera ) spp ., and neither is their somewhat elongate body form. The species of the A cmaeodera faceta , A. bivulnera , A. acanthicola complex are elongate but all are without scales. Clearly, scales are a type of setae, almost always flattened, exhibited in various shapes and sizes, and are likely used as a mechanism of reflecting heat from the body parts as well as possibly "hiding" them from predators on similarly colored plants. The elongate body form is found in many genera of Buprestidae , from all parts of the world, and its derivation and particular function is not understood. Whether understood or not, the elongate 'morphotype' has adaptive survival value because it is found in so many unrelated taxa throughout so much of the world. (e.g. Agrilus spp ., Coraebus spp ., Dinocephalia spp ., Iridotaenia spp ., Mixochlorus spp ., Philandia spp ., Phrixia spp ., Ptosima spp ., Synechocera spp .)