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Journal of the Lepidopterists' Society 43(3), 1989, 229-238

A NEW SUBSPECIES OF COENONYMPHA TULLIA (MULLER)

(NYMPHALIDAE: SATYRINAE) CONFINED TO THE

COASTAL DUNES OF NORTHERN CALIFORNIA

Adam H. Porter

Department of Zoology, University of California, Davis, California 95616

AND

Sterling O. Mattoon

2109 Holly Ave., Chico, California 95926

ABSTRACT. Coenonympha tullia yontocket is described from a single known population confined to the coastal sand dunes north of Crescent City, Del Norte County, California. It is most similar in phenotype to C. tullia eunomia Dornheld, but may be distinguished by wing characters. A population of C. tullia eryngii Hy. Edwards occurs ten kilometers away; these two populations show no clear signs of reciprocal introgression in wing characters. Electrophoretic analysis indicates that yontocket retains the high genetic variability characteristic of other tullia-group taxa, but no diagnostic alleles were found. The high genetic variability is most likely maintained by gene flow from eryngii. Coenonympha tullia subspecies yontocket, eunomia, eryngii, and California Westwood are genetically very similar (Nei's unbiased genetic distance <0.035). The data justify the placement of yontocket as a subspecies rather than a species. This subspecies is a likely candidate for listing as threatened in California; collectors and developers are urged to protect this population from extinction.

Additional key words: Coenonympha tullia yontocket, taxonomy, electrophoresis, ringlets, threatened species.

Investigation of the coastal dunes of northern California has turned up a unique population of the widespread Ringlet butterfly, Coenonympha tullia (Muller). This population occurs in the vicinity of Crescent City, Del Norte Co., and has an ochre ground color; it is wholly contained within the range of C. tullia eryngii Hy. Edwards, a widespread subspecies with a whitish ground color. It is quite similar phe-notypically to C. tullia eunomia described by Dornfield (1967), whose nearest known population is 250 km away in the Umpqua River drainage in southeastern Oregon (Porter & Geiger 1988). This new population flies in the fog belt, and shows the heavy melanization of the wings and body characteristic of butterflies from this type of environment (Hovanitz 1941, McCorkle & Hammond 1988).

Herein, we provide a description of this population as a new subspecies, and justify our taxonomic placement with genetic evidence from electrophoretic analysis. We did not examine genitalic or larval characters: Davenport (1941) indicated that all tullia-group taxa were indistinguishable genitalically despite high levels of intrataxon variability, and description of the immature stages would be of little taxonomic use given our small series and the lack of comparative material.

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Journal of the Lepidopterists' Society

Volume 43, Number 3

231

Coenonympha tullia yontocket, new subspecies

(Figs. 1-3)

Description. Holotype (Fig. 1): male; dorsal ground color dull ochraceous; medium to light gray scaling along the costal and distal forewing margins, extending proximally along the veins. Dorsal hindwing with gray scaling along distal margins, stronger in anal area. Eyespots absent; ventral whitish markings barely visible from above. Both dorsal surfaces strongly melanized subbasally. Ventral forewing ground color deep ochraceous, almost orange; medium band whitish, extending from R veins to Cu2; ground color fades to whitish, then greenish gray in costal and apical regions, becoming strongly suffused with melanized scales; eyespots absent. Ventral hindwing ground color brownish ochre in discal region, fading to greenish gray beyond the median markings. Median band whitish, well marked; absent only between Cux and Cu2. Whitish basal patch present at radial vein. Eyespots absent. Darkened, single marginal line on all wing surfaces, well expressed ventrally. Head, thorax, and ventral hindwing bases covered with long hairs matching ventral hindwing ground color.

Morphological variation (Figs. 2, 3). Forewing length, males: 14-18 mm (n = 65); females: 15-19 mm (n = 10). Spring brood averages slightly larger (males: x = 16.3 mm; n = 52) than fall brood (males: x = 14.7 mm; n = 17). Spring brood: gray scaling dorsally along the distal margins of both wings may be almost absent, but may extend proximally in extreme individuals (n = 2) so that the outer third of the wing is pale gray. Ventral forewing median band whitish; extends from R veins to Cux or Cu2. Single ventral forewing eyespot absent in most individuals, but may be up to 1 mm diameter, unpupilled ochraceous or yellow, or yellow pupilled with black. Ventral hindwing: ground color sometimes obliterated by melanized scaling in discal area; wholly brownish or wholly greenish in some individuals. Median band sometimes weakly expressed between Cux and Cu2, rarely absent below M3 (Fig. 3b). Whitish basal patches often present, connecting to median markings via the costa in extreme individuals (n = 2) (Fig. 3a). Eyespots absent in almost all individuals; rarely up to three, yellow or yellow with black pupils, most likely between CUi and Cu2. Marginal line often double. Females (Fig. 2) tend towards less melanization, broader wings. Fall brood: markings similar to spring brood, more animals with brownish rather than greenish ventral ground color, and more likely expression of ventral basal patches.

Diagnosis. Separable immediately from nearby populations of eryngii by the ochraceous ground color. Separable from eunomia ventrally by stronger expression of the medial markings; from eunomia and ampelos ventrally by the frequent occurrence of basal patches, and dorsally by gray scaling along the veins and outer wing edges.

Distribution. Known only from Del Norte Co., California, among the coastal sand dunes north of Crescent City, beginning at the north shore of Lake Earl and extending north 7.5 km to the south bank of the Smith River (Fig. 4). This area is hereby designated as the type locality. Seemingly suitable habitat between Lake Earl and Point St. George may also be populated by yontocket. Not present in abutting disturbed habitats to the east (mostly cow pastures), or at the dunes north of Areata Bay in Humboldt County, California. Replaced by eryngii 10 km to the east on exposed serpentine hilltops.

Material examined. Holotype: Male, California, Del Norte Co., 4 km W Fort Dick, 8-IX-1979, leg. S. O. & E. Mattoon. Deposited in the Bohart Museum at the University of California, Davis. Paratypes: California, Del Norte Co., 4 km W Fort Dick, end of Kellogg Rd. S to north shore of Lake Earl, 2-VI-1979 (15 males), 30-VI-1979 (4 males) & 8-IX-

Figs. 1-3. 1, Coenonympha tullia yontocket holotype male; (a) dorsal and (b) ventral surfaces. 2, Coenonympha tullia yontocket paratype female; (a) dorsal and (b) ventral surfaces. Unlike this specimen, many females do show basal ventral hindwing patches. 3, Coenonympha tullia yontocket ventral surfaces, showing the extremes of expression of maculation. The reduced pattern of (b) is characteristic of C. tullia eunomia populations.

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Fig. 4. Map showing localities sampled in northwestern California and southwestern Oregon. Note the close proximity of the eryngii population to the type locality of yontocket (inset). Neither subspecies occurs in the intervening cow pastures.

1979 (16 males, 2 females), S. O. & E. Mattoon, leg. These will be deposited in the Bohart Museum, the California Department of Food and Agriculture, the California Academy of Sciences, the Los Angeles County Museum, the Allyn Museum, and the National Museum of Natural History, Smithsonian Institution. Additional material: wing vouchers from specimens used for electrophoretic analysis (29 males, 8 females), collected from the Yontocket Archeological Site at the north end of the population range.

Biology. Flight periods May-July and September-October. Habitat: elev. 2 m; in grassy areas among dunes with coniferous lee slopes and grassy exposed slopes, and among dunes on slightly elevated ground around seasonally marshy sphagnum bogs which fill during the rainy season. 2 females oviposited (5 observations) on dry grass stems (mixed species composition) approx. 2-5 cm above soil in areas free from flooding. Larvae and pupa (n = 2 larvae; 1 pupated) are apparently not different from those of eryngii (n = 8 larvae; 2 pupated). Larval host(s) presently unknown.

Etymology. Coenonympha tullia subspecies are often given American Indian names. This population is dedicated to the memory of the Yontocket tribe, which once had seasonal settlements in these dunes.

In deciding to name this population, we considered two points: (i) is it sufficiently distinct from C. t. eunomia to warrant taxonomic recognition?, and (ii) given that an apparently permanent population of

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C. t. eryngii occurs in serpentine grassland habitat on a hilltop 10 km to the east and within sight of the yontocket population (Fig. 4), should yontocket be given species status? To address these questions, we performed starch gel electrophoresis to provide insights into the genetic relationships among the yontocket population, the nearby eryngii population, a previously studied eunomia population from Riddle, Oregon, and a C. t. California Westwood population from near Myers Flat, Humboldt Co., California. Each of these populations comes from relatively isolated areas of grassland habitat, providing a control on the potential for genetic differentiation resulting solely from variation in local population structure. Previous work has established that eryngii, California, and eunomia are members of a single polytypic species (Porter & Geiger 1988).

Materials and Methods

Butterflies were netted and temporarily stored on wet ice, hand-carried or mailed back to Davis, then frozen alive at — 80°C for storage until analysis. Electrophoretic analysis followed the protocol of Ayala et al. (1972) and Geiger and Shapiro (1986), with one modification: rather than using sponge wicks to complete the circuit between the electrode buffer solutions and the gels, gel molds were used which allowed the ends of the gels to contact the electrode buffer directly. We scored 13 loci: adenylate kinase (AK-1), aldolase (ALDO), fumarase (FUM), glutamic-oxaloacetic transaminase (GOT-1, GOT-2), glycer-aldehyde-3-phosphate dehydrogenase (GAPDH), a-glycerophosphate dehydrogenase (a-GPDH), isocitrate dehydrogenase (IDH-1), malate dehydrogenase (MDH-1, MDH-2), phosphoglucomutase (PGM), phos-phoglucose isomerase (PGI), and superoxide dismutase (SOD-1). Zymograms were scored as described in Porter and Geiger (1988), and data were analyzed using the computer program BIOSYS-1 (Swofford & Selander 1981).

Results

Allelic frequencies for the yontocket, eryngii, and California populations are given in Table 1; allelic frequencies at these loci were previously given for the eunomia population in Porter and Geiger (1988). All populations show high levels of genetic variability characteristic of Coenonympha tullia populations elsewhere (Table 2; Porter & Geiger 1988); this is an indication that the yontocket population has not been through a significant genetic bottleneck in its recent past. Table 3 shows genetic relationships among these populations using Nei's unbiased minimum distance and identity measures (Nei 1978). The phenogram constructed based on these values using UPGMA (Fig. 5; see Sneath &

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Nei's (1978) unbiased genetic identity

0.97 0.98 0.99 1.00 I____________|____________|____________|

i------ California

eryngii

yontocket

eunomia

0.03                0.02                0.01                 0.00

Nei's (1978) unbiased genetic distance

Fig. 5. Phenogram of genetic relationships constructed using the UPGMA algorithm on data from Table 3. Yontocket does not cluster with eunomia, but all populations are genetically very similar.

Sokal 1973 for methodological details) does not group yontocket with eunomia, despite their general similarity in wing characteristics. These distance-identity values indicate a very low level of genetic differentiation overall, corresponding to subspecies-level differentiation in most taxa (Thorpe 1983), including butterflies (AHP unpubl. data; H. J. Geiger, pers. comm.).

Discussion

Neither the yontocket nor eryngii population in Fig. 4 has colonized intervening, non-native grassland presently used for grazing. There is also no clear evidence of introgression in wing pattern traits in the animals we sampled. The pale gray along the veins and wing edges dorsally in yontocket may well be evidence of such introgression, but populations from the Pit River drainage in eastern California, where

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236

Journal of the Lepidopterists' Society

Table 2. Genetic variability statistics for the three populations given in Table 1. Mean number of alleles per locus = xalleles. Percent of loci polymorphic = P. Observed heterozygosity = Hobs. Heterozygosity calculated from Hardy-Weinberg proportions = Hexp. Standard errors in parentheses.

to approximate phylogenetic relationships between species, but these measures can only reflect overall genetic differentiation within a species. Within a species, the degree of differentiation expressed among populations reflects a balance between the forces of natural selection, genetic drift, mutation, and gene flow acting at each locus. The fact that yontocket is more similar to California and eryngii than to eunomia implies that gene flow between yontocket and eunomia is interrupted: it seems unreasonable to consider them consubspecific. This interpretation is also in agreement with the disjunct distribution of these taxa.

The high level of variability in yontocket enzyme characters also requires explanation. The yontocket population probably has an effective breeding population of moderate size, and is likely to be affected somewhat strongly by genetic drift. If yontocket is fully reproductively isolated from eryngii, then exceedingly strong selection on these enzymes is required to maintain such high numbers of alleles; on the other hand, infrequent influxes of eryngii phenotypes could easily maintain this variability. Given that there is evidence of some gene flow between eunomia and eryngii in southeastern Oregon (Porter & Geiger 1988) (the subspecies separated by the greatest geographic distances in the phenogram of Fig. 5), and that yontocket is of intermediate similarity, we think it is wise to place yontocket as a subspecies of tullia unless subsequent studies on reproductive biology demonstrate intrinsic barriers to gene flow. The level of current gene flow between these two adjacent tullia-group populations, based on their present constellations of allelic frequencies, indicates that these populations exchange between four and five breeding individuals every generation on average (Porter, in prep.), further supporting the taxonomic placement proposed here.

The evolutionary origins of the diagnostic yontocket traits are explainable by a number of plausible scenarios (many non-diagnostic traits may be attributable to gene flow from eryngii). The most likely scenario is that these traits arose from eunomia or even columbiana Mc-Dunnough, which may have had more southerly distributions during the last glacial stages. A population of Polites mardon (Edwards) (Hes-periidae) also occurs in Del Norte Co., California, disjunct from nearest

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Table 3. Nei's (1978) unbiased genetic identity (above diagonal) and distance (below diagonal) values between population pairs. Populations given in the text.

known populations in southwestern Washington State (Scott 1986; T. C. Emmel, J. F. Emmel & S. O. Mattoon, in prep.). However, this alone does not explain the high incidence of the basal ventral hindwing patches, a characteristic of populations in the Great Basin and Rocky Mountains. Whether the basal ventral patch is adaptive, ancestral in North America, or exists in yontocket as a result of past gene flow from the east, is unknown. Functionally unrelated traits can clearly have independent geographic ranges within a species. Thus, the conclusions we draw concerning the historical biogeography of tullia-group traits depend largely on whether or not biological species boundaries exist within the complex (and if they do exist, where they are).

We think it is particularly important to recognize the threat of extinction to C. t. yontocket caused by habitat destruction. The southern end of the population distribution occurs in habitat patches within an abandoned gridwork of streets originally intended as a housing development. With the spread of development by the tourist industry around the recently formed Redwood National Park, the yontocket habitat is likely to become attractive to developers of beachfront property—both for private and public use. Given the failure of yontocket to invade adjacent cow pastures, a habitat used by tullia subspecies elsewhere in western North America, it is likely that such development will have severe impact on this population. We urge lepidopterists to refrain from collecting in this fragile ecosystem, and to provide support for groups dedicated to the preservation of this and other threatened taxa along the Pacific Coast.

Acknowledgments

AHP was supported during this study by a grant entitled Cross-disciplinary Studies of Population Structure to the Institute of Ecology at UC Davis from the Alfred P. Sloan Foundation. A Graduate Research Award from the University of California-Davis to AHP partially covered travel to the study area. Rick Harris took the photographs; California Agricultural Experiment Station project CA-D*-AZO-3994-H, Climatic Range Limitations of Phytophagous Insects, to Art Shapiro, funded the electrophoresis; and Brad Shaffer kindly provided laboratory facilities. Chuck Hageman, Ken Hansen, and Eileen Mattoon accompanied SOM when the first series of yontocket was collected.

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Journal of the Lepidopterists' Society

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Received for publication 17 December 1988; accepted 25 April 1989.