Anillinus

Casey, 1918

Species Guides

Anillinus is a of small ground beetles in the Carabidae, comprising more than 60 described primarily from the southeastern United States. Members are blind, wingless, and typically measure 3 mm or less in length. They inhabit deep forest litter, soil, or caves, with many species exhibiting extremely localized distributions. The genus has experienced rapid taxonomic expansion, increasing from 11 known species in 2003 to 63 by 2023, and serves as a valuable model for biogeographic and evolutionary studies of regional biotas.

Anillinus virginiae by (c) Derek Hennen, some rights reserved (CC BY), uploaded by Derek Hennen. Used under a CC-BY license.

Anillinus barberi by (c) Derek Hennen, some rights reserved (CC BY), uploaded by Derek Hennen. Used under a CC-BY license.

Anillinus albrittonorum (10.3897-subtbiol.39.65769) Figure 4 by Sokolov IM, Schnepp KE (2021) A new subterranean species of Anillinus Casey (Carabidae, Trechinae, Anillini) from Florida. Subterranean Biology 39: 33-44. https://doi.org/10.3897/subtbiol.39.65769. Used under a CC0 license.

Pronunciation

How to pronounce Anillinus: /ænɪˈlaɪnəs/

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Identification

within Anillinus are distinguished primarily by characters of the male genitalia (), with secondary characters including shapes of female spermathecae, body size, and relative proportions of body parts. Species group affiliation can be indicated by microsculpture patterns: for example, loweae-group species lack microsculpture on paramedian areas of the head. Identification to species level requires examination of genitalic structures and often geographic provenance.

Images

Appearance

Small beetles, typically 3 mm long or less. Body form adapted for subterranean and litter-dwelling habits. absent; wingless. Specific morphological characters vary by group; for example, the loweae-group exhibits paramedian areas without microsculpture on the .

Habitat

Deep forest litter, under rocks, soil (endogean ), and caves (troglobitic). Habitat preference varies among , with some groups specialized for subterranean environments while others occupy surface litter layers.

Distribution

Southeastern United States, ranging from the Atlantic coast westward to Texas and Oklahoma. Center of diversity in the southern Appalachian Mountains and adjacent upland terrains. Specific documented localities include Great Smoky Mountains National Park (Tennessee/North Carolina), Alabama (Jackson, Morgan, and Jefferson counties), and the French Broad River region. Two Brazilian (A. magnus and A. minor) have been described but their validity is questioned.

Behavior

constrained by physical barriers; exhibit altitudinal stratification influenced by glacial cycles. Extremely localized distributions suggest limited dispersal capability consistent with wingless, subterranean lifestyle.

Human Relevance

Provides valuable biogeographic information for modeling evolutionary systems of regional biotas. Rapid discovery rate makes the a focal group for studies of recent lineage diversification and speciation mechanisms.

Similar Taxa

Other Anillina subtribe generaShare blind, wingless, small-bodied ; distinguished by specific genitalic and microsculpture characters, as well as geographic distribution patterns

More Details

Taxonomic expansion

The remains one of the most incompletely known ground beetle genera in the United States, with count increasing nearly sixfold between 2003 and 2023.

Phylogeographic research

COI gene sequences and aedeagal have been used to reconstruct biogeographic history; however, these data sources sometimes yield conflicting phylogenetic results.

Speciation drivers

Major factors affecting speciation include: division of ancestral ranges due to drainage system changes prior to Pleistocene glaciation; Pliocene-Pleistocene climate cooling with constrained by physical barriers; and Early Pleistocene glacial cycles influencing altitudinal stratification.