Overview

Brief Summary

Neochlamisus beetles are small (around 3 to 4 mm) and nearly cubical. Like other beetles in the Chlamisini (a tribe in the leaf beetle subfamily Cryptocephalinae), adult Neochlamisus beetles have a tuberculate ("warty") dorsal body surface, legs that tuck neatly into depressions, and antennal grooves adjacent to the prosternal process into which the short serrate antennae fit. These features give them the ability to tightly withdraw all appendages to form a compact cylinder and successfully mimic small flower buds, caterpillar droppings, or other forms of debris or excrement. (Chamorro-Lacayo and Konstantinov 2009)

The 17 nominal species of Neochlamisus are distributed in the southwestern United States and Mexico (the five species constituting the velutinus species group) and eastern North America (the 12 species constituting the gibbosus species group) (Karren 1972). The adult beetles feed, mate, and lay eggs on their host plants. Larval development, pupation, and adult emergence all take place entirely on the host plant as well. Thus, other than flying between host plants to find mates and oviposition sites, all life activities occur on the host plant. (Funk 2010)

Neochlamisus beetles and their close relatives use their fecal material to construct cases within which their larvae develop. Females lay individual eggs on host plants and meticulously fashion a protective egg case using plates of their compressed fecal matter. Hatchling larvae cut away the "roof" of this case, but remain within it, turning it upside down and walking with head and legs projecting from this opening, continually expanding it with their own fecal material during growth. Larvae feed on the host throughout development and seal the case opening to the substrate just prior to pupation. (Chaboo et al. 2008; Funk 2010 and references therein) Brown and Funk (2010) specifically examined how fecal cases protect N. platani from attack by other arthropods and discovered an important protective role for host-plant trichomes (plant hairs) incorporated into the case, a novel example of a physical plant defense (trichomes) co-opted by an herbivore.

A range of studies of closely related Neochlamisus forms have provided support for the role of ecologically driven diversification in speciation, i.e., the evolution of reproductive isolation via the divergent adaptation of populations to alternative environments. (Funk 1998; Funk et al. 2002; Funk et al. 2006; Egan and Funk 2009; Funk 2010) Funk (2010) provides a recent thorough review of Neochlamisus biology and investigations into ecological speciation in this group.

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Comprehensive Description

Neochlamisus beetles are small (around 3 to 4 mm) and nearly cubical. Like other beetles in the Chlamisini (a tribe in the leaf beetle subfamily Cryptocephalinae), adult Neochlamisus beetles have a tuberculate ("warty") dorsal body surface, legs that tuck neatly into depressions, and antennal grooves adjacent to the prosternal process into which the short serrate antennae fit. These features give them the ability to tightly withdraw all appendages to form a compact cylinder and successfully mimic small flower buds, caterpillar droppings, or other forms of debris or excrement. (Chamorro-Lacayo and Konstantinov 2009)

The 17 nominal species of Neochlamisus are distributed in the southwestern United States and Mexico (the five species constituting the velutinus species group) and eastern North America (the 12 species constituting the gibbosus species group) (Karren 1972). Neochlamisus appear to be generally univoltine (i.e., have one generation per year). Individuals pass through four larval instars and have an obligate winter diapause (physiological dormancy) that precedes reproduction. Females emerge from this diapause in spring or early summer (depending on latitude and altitude) and proceed to feed, mate, and lay eggs on their host plants. Larval development, pupation, and adult emergence all take place entirely on the host plant as well. Newly emerged adults feed and mate on the host plant until the winter diapause. In the laboratory, development from oviposition through adult emergence lasts around 2 months at 24 °C. (Chaboo et al. 2008) In a typical life cycle on Long Island, New York, adults emerge from diapause in late spring, then feed, mate, and oviposit (lay eggs) on the plant host through early summer. The new generation of adults begins to appear in late summer and these individuals feed and mate before entering diapause in autumn. (Funk 2010)

Neochlamisus beetles belong to a group of leaf beetles that use their fecal material to construct cases within which their larvae develop. Females lay individual eggs on host plants and meticulously fashion a protective egg case using plates of their compressed fecal matter. Hatchling larvae cut away the ‘roof’ of this case, but remain within it, turning it upside down and walking with head and legs projecting from this opening, and continually expanding it with their own fecal material during growth. Larvae feed on the host throughout development and seal the case opening to the substrate just prior to pupation. Thus, other than flying between host plants to find mates and oviposition sites, all life activities occur on the host plant. (Chaboo et al. 2008; Funk 2010 and references therein) Brown and Funk (2005) and Chaboo et al. (2008) provide detailed accounts of fecal case construction and associated behaviors and life history patterns in Neochlamisus casebearers, including oviposition and egg case construction, larval development and case enlargement, pupal case formation, and adult maturation and emergence. In addition to providing a detailed analysis of case architecture and its variation within and among Neochlamisus species, Chaboo et al. (2008) discussed various possible functions of these cases, including providing physical or chemical protection, camouflage, and protection from desiccation. Brown and Funk (2010) specifically examined how fecal cases protect N. platani from attack by other arthropods and discovered an important protective role for host-plant trichomes (plant hairs) incorporated into the case, a novel example of a physical plant defense (trichomes) co-opted by an herbivore.

A range of studies of closely related Neochlamisus forms have provided support for the role of ecologically driven diversification in speciation, i.e., the evolution of reproductive isolation via the divergent adaptation of populations to alternative environments. (Funk 1998; Funk et al. 2002; Funk et al. 2006; Egan and Funk 2009; Funk 2010) Egan et al. (2008) undertook an ecologically comparative genome scan of 447 AFLP loci for 15 pairwise comparisons of populations of the leaf beetle N. bebbianae. Each population in the study was specifically associated with, and adapted to, one of two tree species (Red Maple, Acer rubrum, or Bebb's Willow, Salix bebbianae) (these host-associated populations appear to be in the process of ecological speciation). Egan et al. identified dozens of loci specifically associated with divergent host-related selection, a finding they suggest is consistent with the hypothesis that ecological speciation has a polygenic basis in this species.

Funk (2010) provides a recent thorough review of Neochlamisus biology and investigations into ecological speciation in this group.

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Physical Description

Diagnostic Description

"Neochlamisus Karren, 1972: 932; Type species: Neochlamisus velutinus Karren, 1972, by original designation." (Chamorro-Lacayo and Konstantinov 2009)

"Diagnosis. Length 2.90-4.70 mm, width 2.10-3.68 mm. General body shape cylindrical. Body usually metallic in color. Frons in canthus of eye usually with yellow spots, or if without yellow spots, then elytron with two velvety spots. Frons glabrous. Pronotum and elytra glabrous. Antenna serrate beyond 3rd or 4th antennomeres, 2nd antennomere slightly widened, globose, 5th antennomere smaller than 6th. Pronotum medially elevated, with various bumps. Pronotal base opposite mesoscutellum (posterior pronotal lobe) with well diff erentiated notch. Prosternum posteriorly narrow or explanate with lateral serration. Anterior margin of metasternum concave. Mesoscutellum short, transverse. Metascutellum exposed or concealed. Sutural serration of elytra usually incomplete (suture entire immediately beyond mesoscutellum, followed by well developed serration). Elytral tubercules well developed. Tibiae slightly curved, slightly fl attened, with sharp dorsal edge. Fore- and midtibial apices with spine. Tarsal claw bifi d or appendiculate. Male ejaculatory guide (part of internal sac of aedeagus) asymmetrical, with sheath. Apex of spermathecal duct globosely swollen, wider than rest of pump." (Chamorro-Lacayo and Konstantinov 2009)

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Look Alikes

Lookalikes

"Neochlamisus can be separated from other chlamisine genera by characters of the male genitalia. The male ejaculatory guide is asymmetrical, with a sheath. Among external characters, color of the frons in combination with the presence of velvety spots usually allows for recognition of Neochlamisus (frons on canthus of eye usually with yellow spots, or if without yellow spots, then elytron with two velvety spots)." (Chamorro-Lacayo and Konstantinov 2009)

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Evolution and Systematics

Evolution

Systematics and Taxonomy

Neochlamisus Karren (1972) (Coleoptera: Chrysomelidae: Cryptocephalinae: Chlamisini) is endemic to North America and includes 17 nominal species, in two species groups (Karren, 1972). The velutinus group includes five southwestern species and the gibbosus group includes 12 eastern species. Available molecular phylogenetic results are consistent with the monophyly of Neochlamisus and of the gibbosus group, which apparently emerges from a paraphyletic velutinus group (Funk, 1999). In W.J. Brown’s important taxonomic work on these beetles in the mid-20th century (see references cited in Funk 2010), he described seven gibbosus group species. Some of these had previously been considered single species, but Brown used host association as a clue for finding consistent anatomical populations associated with a particular plant, but for which evolutionary status (e.g. as populations vs. races vs. sibling species, etc.) remained undetermined. Funk (e.g., 2010) refers to Brown’s sibling species as the alder, oak, and willow host forms, respectively. Fieldwork by Funk subsequently established the validity of some sparse and suspect museum host records, yielding recognition of the maple (Acer rubrum) and birch (Betula nigra) host forms (Funk, 1999). Finally, American Hazelnut (Corylus americana)-associated populations that key out to N. bebbianae are considered a sixth host form (D. J. Funk, unpublished, cited in Funk 2010). Thus, Funk (2010) recognizes the following Neochlamisus taxa (see Funk 2010 for host associations):

Twelve species in the gibbosus group: N. assimilis, N. bebbianae (including six host forms: alder, birch, hazel, maple, oak, willow), N. bimaculatus, N. chamaedaphnes, N. comptoniae, N. cribripennis, N. eubati, N. fragariae, N. gibbosus, N. insularis, N. platani, and N. tuberculatus.

Five species in the velutinus group: N. memnonius, N. moestificus, N. scabripennis, N. subelatus, and N. velutinus


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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:28Public Records:10
Specimens with Sequences:16Public Species:4
Specimens with Barcodes:7Public BINs:0
Species:9         
Species With Barcodes:3         
          
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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Neochlamisus

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Barcode data

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Relevance to Humans and Ecosystems

Risks

Risk Statement

Neochlamisus beetles generally exist at modest densities and have rarely been considered economic pests (but see references cited in Funk 2010 for several exceptions).

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Wikipedia

Neochlamisus

Leaf beetles of the genus Neochlamisus are sometimes known as the warty leaf beetles. They are members of the case-bearing leaf beetle group, the Camptosomata. Measuring 3-4 millimeters in length as adults, they are cryptic, superficially resembling caterpillar frass. 17, sometimes 18 species are presently accepted in this genus, all of them occurring in North America (including Mexico; some were previously in the genus Chlamisus.[1]

Contents

Life history

In the spring, female Neochlamisus lay eggs singly on the leaves or stems of their host plant and then form a case of fecal material around each. The larvae remain on the natal host plant and add to and enlarge their fecal cases as they grow. Case enlargement in Neochlamisus is an elaborate process that larvae perform regularly until the case is sealed to the substrate prior to pupation. During this stage of the life cycle, beetles are immobile and are particularly vulnerable to predation. After about twenty days the newly hardened adult cuts a clean circle around the apex of the case, lifts this cap, and flies off to feed and mate. Neochlamisus adults feed and mate on the larval host plant species.[2]

Neochlamisus species are typically very host-plant-specific and most species primarily use but a single host plant genus or even a single species. A rather well-known exception is N. bebbianae which feeds on particular species from six tree genera representing five different plant families. N. bebbianae populations associated with each of these plants are referred to as separate "host forms" and are the subject of ongoing studies of host-associated speciation.[3]

Species

Seventeen species are widely recognised:[4]

Footnotes

  1. ^ Karren (1972), Chaboo et al. (2008)
  2. ^ Brown & Funk (2005), Chaboo et al. (2008)
  3. ^ Brown (1943, 1946, 1952), Karren (1972), Funk (1998), Funk et al. (2002), Chaboo et al. (2008)
  4. ^ "Neochlamisus Karren, 1972". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=719783.

References

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