A new species of the cryptic, minute, wingless, and enigmatic taxon Caurinus, and the second for the subfamily Caurininae,is described from Prince of Wales Island in the Alexander Archipelago, Alaska. It is distinguished from its only congener, Caurinus dectes Russell, 1979b, which occurs 1,059 km southeast in Oregon and Washington, based on external morphology and sequences of the mitochondrial gene cytochrome oxidase II. These two species are probably evolutionary relicts - the only known members of a clade dating to the Late Jurassic or older.
A new species of the cryptic, minute, wingless, and enigmatic taxon Caurinus, and the second for the subfamily Caurininae,is described from Prince of Wales Island in the Alexander Archipelago, Alaska. It is distinguished from its only congener, Caurinus dectes Russell, 1979b, which occurs 1,059 km southeast in Oregon and Washington, based on external morphology and sequences of the mitochondrial gene cytochrome oxidase II. These two species are probably evolutionary relicts - the only known members of a clade dating to the Late Jurassic or older.
Entities:
Keywords:
Boreidae; Caurinus; Mecoptera; Prince of Wales Island; refugium; taxonomy
Russell (1979a, b, 1982) described the monotypic subfamily Caurininae, genus and species PageBreak, known only from Oregon and Washington, and later described by Beutel et al. (2008) as “arguably one of the most bizarre and cryptic species of Mecoptera and endopterygote insects.” Indeed, members of the genus do not key to any order in most keys to insect orders because they lack a produced rostrum, typical of the order Mecoptera, and lack the diagnostic traits that would place them within any insect order containing flightless adults with rudimentary or vestigial wings. However, they do share with members of the family Boreidae a very distinctive wing morphology and sexual dimorphism in which the adult females are nearly wingless while the males bear shortened scissor-like wings, useless for flight, that bear spines for grasping females during mating. The placement of within the Mecopteran family Boreidae as the sister taxon to the Boreinae ( 26 spp., 2 spp. [Penny 2013]), is apparently well established based on morphological study (Russell 1979a, b, Beutel et al. 2008, Friedrich et al. 2013) and molecular phylogenetics (Whiting 2002). However, despite recent efforts, the genus remains enigmatic due to its preponderance of plesiomorphic and autapomorphic traits (Beutel et al. 2008). The close relationship of the Mecoptera with the fleas, order Siphonaptera, is of particular evolutionary interest (Grimaldi and Engel 2005, Whiting 2002, Trautwein et al. 2012).It was therefore with some excitement that we began accumulating specimens from a large sampling project on the northern end of Prince of Wales Island, Alaska, some 1,059 km from the known range of Russell. Herein we describe this new species.
Specimen data (n=50 lots). Also available online at http://arctos.database.museum/saved/Caurinus-spp via Arctos. Geocoordinates are in WGS84 datum. PoW = Prince of Wales Island. * = holotype male , with genitalia everted and COII gene sequenced. All other specimens are paratypes. W-screen = wet screen, Hab. = habitat. Habitat type codes: T2 = thinned secondary growth, 2= young secondary growth (unthinned), 2o = old (80yr) secondary growth, CC = clearcut, CCe = clearcut / forest ecotone, OG = old growth, AH = alpine heath. Date1 and Date2 = start and stop dates for trap samples.
Sixteen sites at which specimens were found, north end of Prince of Wales Island, Alaska. Table 1 lists site and specimen data, also available online at http://arctos.database.museum/saved/Caurinus-AK. TL = type locality.
Specimen data (n=50 lots). Also available online at http://arctos.database.museum/saved/Caurinus-spp via Arctos. Geocoordinates are in WGS84 datum. PoW = Prince of Wales Island. * = holotype male , with genitalia everted and COII gene sequenced. All other specimens are paratypes. W-screen = wet screen, Hab. = habitat. Habitat type codes: T2 = thinned secondary growth, 2= young secondary growth (unthinned), 2o = old (80yr) secondary growth, CC = clearcut, CCe = clearcut / forest ecotone, OG = old growth, AH = alpine heath. Date1 and Date2 = start and stop dates for trap samples.Sixteen sites at which specimens were found, north end of Prince of Wales Island, Alaska. Table 1 lists site and specimen data, also available online at http://arctos.database.museum/saved/Caurinus-AK. TL = type locality.The majority of specimens (35/37) were collected in perhumid rainforest dominated by Sitka spruce (PageBreakPageBreak), western hemlock (), lodgepole pine ( var. contorta), Alaska yellow cedar (), red cedar (), and red alder () (Fig. 2). Of 24 sites sampled in the Tongass National Forest project, was found in 14 sites. Fifteen specimens were found in six of six sampled old growth sites, eleven in three of six sampled thinned secondary growth sites, seven in four of six sampled clear cuts, and one in one of six sampled unthinned secondary growth sites. One additional specimen was found in an ecotone next to a clear cut that was not part of the 24 structured sampling sites. The null hypothesis of being equally trappable in all four habitat types: old growth, thinned secondary growth, unthinned secondary growth, and clear cuts, (ignoring the ecotone), is rejected (Chi2 = 12.59, df=3, P=0.0056). These animals are less trappable in unthinned secondary growth sites than expected under the null, and more trappable in old growth and thinned secondary growth sites than expected under the null.
Figure 2.
Habitats of
A Habtiat of type locality, thinned secondary growth with 18 ft. spacing between trees, 55.88433, -132.89734
B example of old growth habitat in which specimen UAM:Ento:204239 was found, 55.88602,-132.8607
C example of clearcut, a habitat type in which seven specimens were found, 55.872, -133.06523
D example of treeless, alpine heath – tundra in which two specimens were found, 55.58818, -132.88881.
Habitats of
A Habtiat of type locality, thinned secondary growth with 18 ft. spacing between trees, 55.88433, -132.89734
B example of old growth habitat in which specimen UAM:Ento:204239 was found, 55.88602,-132.8607
C example of clearcut, a habitat type in which seven specimens were found, 55.872, -133.06523
D example of treeless, alpine heath – tundra in which two specimens were found, 55.58818, -132.88881.Although boreids are considered winter active insects, our projects were restricted to the summer months. We caught more or less evenly throughout the period of sampling (mid May – mid August) (Table 1).
Results from molecular analyses
DNA sequence characteristics. The final alignment of the DNA sequences (11 sequences, 2 outgroup sequences) was 639 base pairs long with 491 constant sites, 21 variable but parsimony-uniformative sites, and 127 parsimony informative sites. Among the sequences there were 604 constant sites and 35 parsimony informative sites. Of these 35 variable sites between the species, 34 were binary with all specimens of each species sharing the same base differing from the other species. As expected, most (29) of these variable sites were third codon positions, with six variable first codon position sites, and zero variable second codon position sites. The null hypothesis of homogeneity of base frequencies across taxa was not rejected by a Chi-square test performed in PAUP*4.0b10 (Chi2=27.5, df=36, P=0.85) (Swofford 2003). These sequences are available from Genbank (accession numbers KF282717 through KF282727) and the aligned NEXUS and tree files are available from TreeBase (http://purl.org/phylo/treebase/phylows/study/TB2:S14415) under study Accession number 14415.The species are 98.5% identical in their inferred COII amino acid sequences (209 of 212 amino acids are identical). The three amino acid replacements are as follows: The 113th site of the amino acid translation is an Alanine (nonpolar) shared by all seven specimens but is a Threonine (polar) in all five specimens; at the 114th site an Aspartic acid (acid polar) shared by all seven specimens is a Asparagine (polar) in all five specimens; and at the 148th site an Isoleucine (nonpolar) shared by all seven specimens is a Valine (nonpolar) in all five specimens.All seven share identical COII nucleotide sequences whereas only three of the share identical sequences, the fourth differs at one site (0.156% divergent) from the other three . The two species are 5.44% divergent from each other (uncorrected “p” distance). The two outgroup species are 3.9% divergent from each other, and 21% () to 20% () divergent from . The COII GenBank record of (AF424001.1) is 21.7% divergent from the seven we sequenced. Using the parameter values from the Garli analysis (see below) to set the HKY+G model in PAUP*4.0b10 allowed the estimation of distances corrected for multiple hits: the two species are 7.17% divergent from each other. The two outgroup species are 5.6% divergent from each other, and 106.7% () to 103.5% () divergent from .Bayesian Analysis. Tracer reported auto-correlation times of 1027 and 1015 for the two runs with Effective Sample Sizes for all parameters of each run above 7000 (with samples from both runs combined, the ESS of each parameter was above 15,000). Parameter estimates of both runs combined were as follows: the harmonic mean of the estimated marginal likelihood was –1515.7, tree length 0.692, the transition/transversion rate ratio (kappa) 6.59, pi(A) 0.356, pi(C) 0.151, pi(G) 0.102, and pi(T) 0.391 with the alpha shape parameter at 0.258.Garli Analysis. The 1000 bootstrap replicate analysis resulted in similarly strong branch support values as the Bayesian analysis (Fig. 3). One hundred non-bootstrap replicates were completed, the best tree of which was found in 96 of the searches and was identical in topology to the Bayesian tree (Fig. 3) with a -lnL of 1476.75, tree length of 0.858, and parameter values of: K parameter 8.789, ti/tv 3.321, pi(A) 0.3596, pi(C) 0.1481, pi(G) 0.0991, and pi(T) 0.3933 with the alpha shape parameter at 0.1733.
Figure 3.
Inferred phylogeny from Bayesian analysis. Each terminal is a single specimen with the UAM cryovial barcode of its DNA extraction indicated by a six digit number. Branch support is indicated as estimated posterior probability from the Bayesian analysis first and maximum-likelihood bootstrap percentages second. Branch lengths are proportional to the number of substitutions per site as reconstructed by MrBayes 3.2. Specimen 242224 is the holotype of
http://arctos.database.museum/guid/UAM:Ento:142986. The remaining three specimens correspond to the following paratypes in Table 1: 242222 (UAM:Ento:135818), 242225 (UAM:Ento:159119), and 242226 (UAM:Ento:154335).
Both the Bayesian and maximum likelihood analyses found strong support for reciprocal monophyly of both species (Fig. 3).Inferred phylogeny from Bayesian analysis. Each terminal is a single specimen with the UAM cryovial barcode of its DNA extraction indicated by a six digit number. Branch support is indicated as estimated posterior probability from the Bayesian analysis first and maximum-likelihood bootstrap percentages second. Branch lengths are proportional to the number of substitutions per site as reconstructed by MrBayes 3.2. Specimen 242224 is the holotype of
http://arctos.database.museum/guid/UAM:Ento:142986. The remaining three specimens correspond to the following paratypes in Table 1: 242222 (UAM:Ento:135818), 242225 (UAM:Ento:159119), and 242226 (UAM:Ento:154335).
Male (in UAM), here designated, labeled “USA: Alaska, Prince of Wales Is. Hatchery Ck.4, 30 May-14 June 2010, 55.88433°N, 132.89734°W ± 26m, 82m elev., thinned secondary growth with 18 ft. spacing between trees, pitfall 3, J. Stockbridge, C. Bickford”, / “HOLOTYPE Sikes & Stockbridge 2013 UAM:Ento:142986” [red paper]. http://dx.doi.org/10.7299/X7GH9J4M
Paratypes.
36 Specimens (Table 1). The following 17 paratypes will be deposited in the collections indicated: male UAM:Ento:159146, female UAM:Ento:142985, female UAM:Ento:235025 (CAS); male UAM:Ento:229945, female UAM:Ento:235024, female UAM:Ento:229942 (OSAC); male UAM:Ento:235026, female UAM:Ento:203239, female UAM:Ento:203011 (PMJ); male UAM:Ento:167053, female UAM:Ento:229944, female UAM:Ento:235023 (SEMC); male UAM:Ento:217990, female UAM:Ento:221708, female UAM:Ento:159120 (USNM); male UAM:Ento:229943, female UAM:Ento:230091 (MTEC), and the 19 remaining in UAM.
Type Locality.
USA: Alaska, Prince of Wales Is. Hatchery Ck, 55.88433°N, 132.89734°W ± 26m, 82m elev. (Fig. 1, 2A).
Measurements.
Restricted to specimens with retracted genitalia (3 males, 10 females), length, min. – max., mean ± SD: male 1.58–2.02, 1.74 ± 0.24 mm, female 1.64 – 2.00, 1.79 ± 0.13 mm.
Diagnosis.
Circumference of eye of males comprises 31-35 (n=3) ommatidia ( males have 38–39, n=3). Scanning electron microscope-level resolution is required to obtain reliable counts (Fig. 4). Female 8th sterna without a median notch (n=10), or with a shallow median notch (n=5) (Fig. 5A, C, 6C, D). females have a shallow median notch or a pronounced median notch (Fig. 5B, see also Russell [1979b] fig. 10). This is visible at 40× and higher magnification.
Figure 4.
Eye of A male (UAM:Ento:230088) showing 38 ommatidia around circumference of right eye, dorsal is to the left, and B male (UAM:Ento:202344) showing 35 ommatidia around circumference of left eye, dorsal is to the right. Scale bar = 50 µm.
Figure 5.
A ventral view of female (UAM:Ento:203239) showing 8th sternum with shallow median emargination / notch, scale bar = 500 µm B ventral view of abdomen of female (UAM:Ento:228458) showing 8th sternum with a pronounced notch, scale bar = 200 µm C ventral view of abdomen of female (UAM:Ento:203011) showing 8th sternum with shallow emargination / notch, scale bar = 200 µm.
Figure 6.
Female (UAM:Ento:159119) that had been cleared in KOH. A lateral view (broken abdomen), scale bar = 2 mm B face, scale bar = 0.5 mm C dorsal view, scale bar = 2 mm D ventral view, scale bar = 0.5 mm.
Eye of A male (UAM:Ento:230088) showing 38 ommatidia around circumference of right eye, dorsal is to the left, and B male (UAM:Ento:202344) showing 35 ommatidia around circumference of left eye, dorsal is to the right. Scale bar = 50 µm.A ventral view of female (UAM:Ento:203239) showing 8th sternum with shallow median emargination / notch, scale bar = 500 µm B ventral view of abdomen of female (UAM:Ento:228458) showing 8th sternum with a pronounced notch, scale bar = 200 µm C ventral view of abdomen of female (UAM:Ento:203011) showing 8th sternum with shallow emargination / notch, scale bar = 200 µm.Female (UAM:Ento:159119) that had been cleared in KOH. A lateral view (broken abdomen), scale bar = 2 mm B face, scale bar = 0.5 mm C dorsal view, scale bar = 2 mm D ventral view, scale bar = 0.5 mm.
Description.
Body length 1.5–2.3 mm, flea-like in lateral view, color reddish brown, sparsely pubescent, strongly sclerotized (Fig. 6). Rostrum absent or reduced. Clypeolabral suture present. Clypeus divided into post and anteclypeus. Penultimate maxillary palpomere enlarged and club shaped. Antennal insertion lateral, widely separated. Ocelli absent. Antennae with sixteen antennomeres and a single countersunk sensilla on antennomeres 4, 5, and 6 (Fig. 7). Mandible with two subapical teeth (Fig. 6B). Male forewings extend to end of first abdominal segment, with six bristles (Fig. 8A), hindwings absent. Female forewings pad-like, hindwings absent. Tarsi five segmented, tarsal claws present. Pilosity absent. Abdomen widest at segments 4 and 5, segments 2-6 fused, annular. Male 8th tergum and sternum not fused. Male 9th tergum and sternum not fused. Genitalia normally concealed in both sexes. Male gonostyles flattened, deeply incised (Fig. 8B).
Figure 7.
Base of antenna showing sensilla on antenomeres 4, 5, and 6. A female (UAM:Ento:230088), B female (UAM:Ento:203237); sen = sensilla, scale bars = 20 µm.
Figure 8.
SEM images of male (UAM:Ento:204239), scale bars = 100 µm A dorsal view showing wings B evertedgenitalia showing paired gonostyles, oblique lateral view.
Base of antenna showing sensilla on antenomeres 4, 5, and 6. A female (UAM:Ento:230088), B female (UAM:Ento:203237); sen = sensilla, scale bars = 20 µm.SEM images of male (UAM:Ento:204239), scale bars = 100 µm A dorsal view showing wings B evertedgenitalia showing paired gonostyles, oblique lateral view.
Variation.
One male (UAM:Ento:231726) has 7 bristles on its right wing, as a result of a very small extra basal bristle, and six on its left.
Geographic Distribution and Habitat.
This species is only known from the northern half of Prince of Wales Island within a region about 45 km in size (Fig. 1). It was collected in forest habitat of various stages: old growth, secondary growth (thinned and unthinned), and young clear cuts; in addition to two specimens caught in alpine heath habitat and one in an ecotone of clearcut / secondary forest. The species is not restricted to lowland forests, nor to old growth forests.
Etymology.
“Tlagu”, pronounced “tlu-gu”, is derived from the Alaska Native tribal language Tlingit meaning “ancient, forever” (Crippen 2013) or “old, from the past” (Edwards 2009). Bierhorst (1985) provided this elaboration: “Among the Tlingit, for example, there are two kinds of stories, tlagu (of the long ago) and ch’kalnik (it really happened).” We name this species in honor of the place it occurs, its people, and history, in addition to the apparent great age of the genus .
Discussion
Diagnostic characters were not easily found. These species are very similar phenotypically. The use of ommatidia counts around the circumference of the eyes of males (females we examined overlapped in these counts) is certainly not an ideal character because it is limited to one sex and requires SEM imaging to obtain accurate counts. In part because of this difficulty, and the rarity of specimens, our sample sizes for the assessment of this character are suboptimal. Despite these small sample sizes (n=3 for each species) the means differ significantly based on an unpaired, two-tailed student’s t-test (p = 0.0142). We hope that ongoing morphological study of the Mecoptera by Rolf Beutel and others (e.g. Beutel et al. 2008) will better document variation between and within these species.During our examination of characters we compared both species for the paired cupuliform and countersunk antennal sensilla described by Beutel et al. (2008, fig. 3D) as occurring on the distal part of antennomeres 3 and 4. We found these on antennomeres 4, 5, and 6 (Fig. 7) but could not find them on antennomere 3 of either species. Also, we found the countersunk sensillum but not the cupuliform sensillum. We studied 5 specimens of and 5 of , 3 males and 2 females of each, and were able to see sensilla on 2 female and 1 male and 2 female but on no others. A shorter type of setae with a thicker apex is present near the countersunk sensilla (Fig. 7) which were also visible on those specimens on which we did not find sensilla. This lack of confirmation is likely due to the fixed positioning of the specimens for SEM imaging hiding the sensilla from view, although infraspecific variation and absence cannot yet be eliminated as explanations. The lack of sensilla on antennomere 3 of raises the possibility that there are multiple species under the name .We examined the gonostyles of the males (Fig. 8B) for diagnostic characters. These complex structures may still hold diagnostic potential. In particular, the apex of the PageBreakgonostyle’s setose basal tooth appeared tapered in and truncate in . However, we were not able to confirm this state was constant in each species. The shape of the upper blade and the pattern of scale-like ridges on the upper blade also appeared to differ. Further study indicated these differences were probably due to differences in the available angles of viewing within the SEM.We do not know the explanation for the very large COII difference (21.7%) seen between the GenBank record and our own sequences of seven specimens. Both samples were made by the same collector, and author of the species, L. Russell, from the type locality. The GenBank record for the COII is 4.5% different from that of the GenBank record for (AF424023.1) from the same study (Whiting 2002) which suggests possible contamination or data mixup. Given the ambiguity of the GenBank record’s accuracy we decided to exclude it from our analyses.The two specimens recovered from the treeless alpine tundra site appear to violate characterizations of PageBreak being a forest associated lineage. However, is often recovered from forested and open rocky sites with the common moss , which represented 20% of the total vegetation at the alpine site (K. LaBounty pers. com.). That occurs in clear-cuts and secondary growth sites suggests it is not a habitat specialist. However, within the secondary growth sites in which was found, it was significantly more common in thinned sites (n= 11) than in unthinned (n=1). The former have been opened by the Forest Service program TWYGS (Tongass Wide Young Growth Studies) in which the trees have been thinned to encourage old-growth conditions whereas the latter habitats are closed-canopy and dark due to the overcrowding of even-aged trees. This does raise questions about the feeding and breeding ecology of . Russell (1979b, 1982) documented as a specialist on epiphytic and terrestrial leafy liverworts (Jungermanniales). We lack adequate data on the bryophyte communities of the lowland forested sites to assess whether shows the same bryophyte associations as . In particular, seven specimens (19% of our total catch) were found in recently deforested clear cuts, which are likely to have highly disturbed bryophyte communities.Another notable difference between these species may be their phenology. Russell (1982) describes adult as primarily active during the winter (October – April), but reappearing in unseasonably wet, cool weather during the summer. This contrasts with our findings of summer presence of adult . Of course, could also be active year-round but our sampling regime would fail to detect anything but summer activity.Various plausible scenarios exist to explain the 1,059 km range disjunction and presumed allopatric speciation within this genus of wingless mecopterans. Either or both populations could be the result of ancient (paleoendemism) or recent (neoendemism) dispersal from the other population or elsewhere (now extinct, or as yet unfound). Such dispersal could be as simple as the ancient transport of -laden bryophytes by a bird. Given the genetic divergence between the populations, human transport is unlikely because it would be too recent. Alternatively, and we think more likely, both populations may be relicts of an ancient, and much larger population, with subsequent intervening extinction (paleoendemism). A multi-locus population genetics analysis with incorporation of data regarding the region’s geological history would be needed to test these alternatives. Finally, these animals are not easily found and undetected populations may occur in intervening British Columbia.Prince of Wales Island was mostly buried under an ice sheet during the maximum of the late Wisconsin glaciation 26,000 to 13,000 14C years BP (Carrara et al. 2007) and had been repeatedly buried by ice during the Pleistocene. However, considerable biological and geological evidence suggests that ice-free refugia may have existed during this time, allowing many diverse taxa to continue to evolve in relative isolation, and re-seed the region after deglaciation (Carrara et al. 2007). Of 108 mammal species or subspecies occurring in southeastern Alaska, 27 are endemic to the area (Cook et al. 2001). The known locations of are in regions that were reconstructed as under ice by Carrara et al. (2007, fig. 3). Post deglaciation dispersal to these sites from ice-free refugia is the most likely explanation. This suggests, and it would be likely regardless, that is more widely distributed than we have documented.Despite their strong phenotypic similarity, the weight of the evidence supports the conclusion that these separate populations are not conspecific. Their mtDNA sequences being 7.17% divergent (corrected for multiple hits) suggests they have been isolated for probably less than 10 million years (Klicka and Zink 1997, Papadopoulou et al. 2010). Regardless, they have probably been isolated for longer than PageBreak and have been isolated from each other. This degree of separation eliminates a late Pleistocene (100,000–250,000 YBP) speciation event hypothesis. The corrected genetic distances between and (over 103%), indicate the COII gene is fully saturated with multiple hits at this level of comparison, and support the hypothesis of Russell (1979b) that is a lineage of great age and not an example of relatively recent evolutionary reversal that would make the Boreinae paraphyletic.This suggests the split between the genus and the remaining boreids likely predates the oldest confirmed boreid fossil, Sukatsheva & Rasnitsyn, of the Late Jurassic (Grimaldi and Engel 2005) which appears to be a boreine due to its size and external ovipositor, although it lacks the produced rostrum typical of extant species (Russell pers. com.). If confirmed, such a great age (>145 Ma) for a genus of two extant species would make the lineage an evolutionary relict and its species certainly deserving of conservation attention (Habel and Assmann 2010, Naskrecki 2011).
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