BRANCHIOPOD DIVERSITY IN SAN DIEGO COUNTY, CALIFORNIA, USA

MARIE A SIMOVICH, Biology Department. University of San Diego, and San Diego Natural History Museum, San D iego , CA 921/0

MiCHAEL FUGATE, Biology Department. University of California. Riverside. CA 92521

1992 TRANSAOlONS OF THE WESTERN SEalON OF THE WILDLIFE SOCIETY 28:6-/4

Abstract: Branchiopod crustaceans (fairy, clam. and tadpole shrimp) are common faunal elements in ephemeral aquatic habitats. All arc adapted to the temporary presence of water and to specific sets of environmental parameters (e.g., salinity. temperature, pH). These organisms arc often overlooked due to the limited time they and their habitat exists. San Diego County provides a diversity ofephemeral habitats ranging from coastal vernal pools to desert playas. However. only one branchiopod species has previously been reported from the area . Our studies have revealed a diverse fauna of four specie s of fairy shrimp in three families , three species of clam shrimp in two families, and one species of tadpole shrim p. Two of the fairy shrimp have range s almost entirely restricted to San Diego County and are threatened with extinction due to habitat loss.

The tremendous loss of temporary aquatic habitats obs. and D. Belk, pers . comm.). The Conchostraca and worldwide has increased interest both in their unique and Notostraca have not been recently reviewed but are highly endemic flora and fauna and in their conservation represented by at least eightand four species, respectively (Jain 1976. Holland 1978. Dimentrnan 1981. Holland (Wootton and Mattox 1958, Lynch 1966 , Sassaman and Jain 1981. Herbst 1982. Jain and Moyle 1984. Belk 1989, Ahl1991 , Sassaman 1991, unpubl. data). Fiveof and Eriksen 1990, Belk et al. 1991, Jeffries 1991, Shoup the seven endemic fairy shrimp have only recently been 1991). The loss of habitat poses a threat not only to the described., and due to urban and agricultural expansion species living in the pools, some ofwhich have potential most warrant consideration as threatened or endangered uses for humans for food (Cheatham 1984, Sorgeloos et (Eng et al. 1990). al. 1986, Mitchell 1991), but also to numerous species of San Diego County specifically has experienced a waterfowl that feed on temporary pool organisms (Krapu tremendous loss of habitat and the review of Eng et al. 1974, Swanson et al. 1974, Driver 1981, Miiller 1987, (1990) and the subsequent description ofa new endemic Shoup 1991). fairy shrimp (Fugate, in press) make obvious the lack of The branchiopods in the orders Anostraca (fairy information on the county'sbranchiopod fauna. Prior to shrimp and brine shrimp), Conchostraca (clam shrimp) this study, only one branchiopod species was reported and Notostraca (tadpole shrimp) are often the dominant from San Diego County (Balko and Ebert 1984, Ebert fauna ofthe early successional stages of ephemeral water and Balko 1987, Eng et a:r 1990). Due to the diversity (Sublette and Sublette 1967, Ebert and Balko 1984, of habitats in the county, it was thought more species Dodson 1987) and have been used extensively for might be present. The present paper presents information aquaculture (Belk et al. 1991). Many branchiopods have on the distribution and biology ofbranchiopods from San specific habitat requirements (e.g., temperature, pH, Diego County. alkalinity, etc .) (Shantz 1905, Prophet 1963, Procter 1%4, Horne 1967, Moore 1967,Broch 1969, McCarraher STUDY AREA 1970, Brown and Carplan 1971, Hillyard and Vinegar Eng et al . (1990) divided California into eight 1972, Alexander 1976, Belk 1977a, Moore 1979, Donald regions, two of which are represented in San Diego 1983, Thiery 1987, Brach 1989, Eng et al. 1990 ). Due County: the South Coast Mountains, occupying the to these requirements, they, like other ephemeral pool western two-thirds of the county, and the Colorado plants and animals, are prone to endemism (Eng et al. Desert, occupying Anza Borrego State park and the 1990, Mura 1991) . surrounding area. Eight South Coast Mountain sites California's temporary inland waters and saline were sampled (Fig . 1,Table 1). These sites are primarily lakes support a diverse. but poorly studied branchiopod vernal pool complexes in various states of disturbance fauna(Wootton andMattox 1958, Lynch 1%6, Sassaman (Bauder 1986, Zed1er 1987). These pools typically fill 1989, Eng et al. 1990, Ahl 1991, Sassaman 1991). The during winter or early spring rains. Four COlorado twenty described species of Anostraca in California, Desert sites were sampled (Fig. 1, Table 1). These sites seven of which are endemic. comprise forty-four per cent are primarily playas except the Mortero Wash site which of the total species diversity in the United States (Eng et is a pool formed in a desert wash. The desert sites can fill al. 1990, Belk and Serpa 1992, Fugate in press) and from either cool winter rains or warm summer another is currently being described (M. Fugate, pers . thunderstorms,

6 TRANS. WEST. SECT. WILDL SOc. 28: 1992 Branchiopod D iversity · Simovich and Fugate 7

METHODS species hatches from 0-25°C, tolerates temperatures up Samples have been collected since 1988 by either to 36°Casan adult (Belk 1977a), and is found overa wide sampling with aquatic dip nets after rainfall filled pools range of pH and salinity values (McCarraher 1970, Eng or by hydrating soil samples in the laboratory. Soil et al. 1990) . Development times in the laboratory or the samples consisted of sediment from the top 2-5 em ofdry field can beas short as 8 to 12 days (Donald 1983, Fugate pools. These samples were washed through 500 and 180 unpubl. data) at some temperatures. um sieves and the soil in the 180 um sieve was examined Bran chinecla lindahli was the only species previously for branchiopod eggs. The eggs of most branchiopods reponed from San Diego County (Balko and Eben 1984, can be identified to genus and in some cases to species Eben and Balko 1984, Eng et al. 1990) . However, (Alonso and Alcarez 1984. Mura 1986, 1991, Mura and reexamination (by M. Fugate and D. Belk) ofthe voucher Thiery 1986, Thiery and Gasc 1991). Samples with eggs specimens from these studies has shown them to be were hydrated by placing 150 rnl of sediment in a 10 Branchinecta sandiegoensis. The species was gallon aquarium and adding 251ofdeionized water. The subsequently found in desert playas whichalso contained aquaria were continuously illuminated with fluorescent combinations of Thamnocephalus platyurus, Eocyzicus light and"grow lights" , aerated vigorously for 24 hours, digu eti and/or Triops newberryi (Table 1). Branchinecta stirred and then gently aerated. Upon hatching, shrimp lindahli was also found in a single road rut on Naval Air were fed small amounts of baker's yeast until they Station Miramar and a few individuals in one rut on Del reached a length of at least one centimeter at which time Mar Mesa (Table I, Fig. 1). they were fixed or frozen. Hydrations were conducted at Branchinecta sandiegoensis Fugate, although temperatures, between 10° and 25° as these temperatures collected in 1962 and deposited in collections of the bracket the ranges of species inhabiting San Diego (Eng United StatesNational Museum, Washington, D.C., was et al. 1990 , Sirnovich, unpubl. data). misidentified as B. lindahli, This species was recognized Branchiopods were identified by comparison with as a new species in 1990 and was recently described original descriptions or re-descriptions of species, but (Fugate 1992 in press). Only limited information on its species identification isproblematic in both Conchostraea physiological requirements and life history exists. It was and Notostraca (Belk 1989, Sassaman 1991) . The found usually in shallow « 30 ern) pools, predominantly species ofthe clam shrimpfamily Cyzicidae, for instance, on mesas, after winter and spring rains, at water have often been described using size-dependent characters temperatures of 1O-26°C. Our preliminary laboratory without accompanying development studies and we have results suggest that the species can hatch at cool chosen to accept the earliest name recorded in the temperatures (1O-15°C) (un publ. data). literature for species, consistent with the International This species is currently known only from San Diego Code of Zoological Nomenclature. Animals were fixed County samples (Table!, Fig. I ) and from Valle de las in 10% formalin or Bouin's solution andthen transferred Palmas, Baja California None, Mexico (presumably the to70%ethanolor were frozen for protein electrophoresis. same mesa system) . It iscommonly the only branchiopod Voucher specimensand their collection data are available species in a pool, but was found in the same two pools as in the UDiversity of San Diego Branchiopod Collection. Streptocephalus woottoni and Cyzicus californicus at Otay Mesa and in a pool with S. woottoni at Naval Air RESULTS AND DISCUSSION Station Miramar . In these mixed pools, B. sandiegoensis Eight branchiopod species were found in San Diego was found earlier in the season than the other species. County: four fairy shrimp species in threefamilies, three Also, a few B. lindahli «0.1%) were found with it in one clam shrimp species in two families, and one tadpole rut on Del Mar Mesa. shrimp (Table 1).Present collections may underestimate TheU.S. Fish and Wildlife Service hasbeen petitioned the total diversity in the county, due to both the limited to list B. sandiegoensis as an endangered species (D. sampling of pools and the specific requirements of Hogan, pers. comm.) due to its restricted distribution and individual species which may prevent all the species the loss of approximately 97% of this habitat in San present from hatching after a natural filling or hydration. Diego (E. Bauder, T. Oberbauer, pers. comm.). Streptocephalus woottoni Eng, Belk and Eriksen is Anostraca (Fairy Shrimp) California's most restricted endemic fairy shrimp. This Branchine cta lin dahli Packard is common species was described from five large (>750 rn")and deep throughout western North America (Eng et al. 1990, (>30 em) pools near Murrieta in Riverside County (Eng Maeda-Martinez 1991) and is found in a wide variety of et al. 1990). At these sites, Branchinecta Iynchi and B. habitats from roadside ditches to playas and prairie lindah Ii were present as well ; however, S. woottoni potholes, but rarely in undisturbed vernal pools . This appeared later. Eng et al. (1990) suggested that it Otay 8 Branchiopod Diversity· Simovich and Fugate TRANS. WEST. SECT. WILDL SOc. 28: 1992

North

:;: -e rn ~ r + n o c z :1

Scal e I I 9km 18km

Fig. 1. Distribution of sampling sites in San Diego County, 1. Del Mar Mesa, 2. Arroyo Sorrento, 3. Na val Air Station Miramar, 4. La Jolla., 5. Mission Trails, 6. Otay Mesa, 7. San Marcos, 8. Ramona, 9. Clark Dry Lake, 10.Blair Valley, 11. Benson Dry Lake, 12. Monera Wash.

hatched at warmer temperatures than the endemic these pools . Their appearance seems to be sequential branchinectids. Our laboratory results suggest that it with B. sandiegoensis appearing first. In all three pools tolerates a range of temperatures (at least 1O-25°C) and the emergent plant Eieochariswas present, as also noted that it has a development time of a month or more in some of the Riverside County pools sampled by Eng (unpubl. data) . The longer developmental time may et al. (1990). account for its restriction to deep pools, rarity, and late The U.S . Fish and Wildlife Service has proposed appearance. this species for listing as an endangered species (F .R ill San Diego County the species was found in one 56:57503) due to its limited distribution and the threat of pool at Naval Air Station Miramar and in two pools on development at the sites in Riverside and San Diego OtayMesa (Table I, Figure 1). The Miramar vernal pool Counties. The Naval Air Station Miramar site is currently is large and deep (>80 ern) and has been disturbed by the only site even nominally protected through federal vehicles. The Otay pools are slightly smaller but again ownership. deep (>30 ern). These pools have been modified for cattle Thamnocephaius platyurus Packard ranges from use and contained water into the summer of 1991. At Wyoming and Missouri toCentral Mexico andthroughout both sites. B. sandiegoensis eggs were present, but we the southwest (Belk 1975, Maeda-Martinez 1991), but is have not observed adults of the two species together in known from only a few sites in southern California (Eng TRANS. WEST. SECT. WILDL SOc. 28: 1992 Branchiopod Diversity· Simovich and Fugate 9

Table 1. Distribution of branchiopods in San Diego County (an X denotes the species is present).

Anostraca Conchostraca Notostraca

Sampling Location BRSA' BRLI STWO' THPL ElITE EODI CZCN TRNE

South Coast Mountains I. Del Mar Mesa X X 2. Arroyo Sorrento X 3. Naval Air Station Miramar X X X 4. La Jolla X 5. Mission Trails X 6. Otay Mesa X X X 7. San Marcos X 8. Ramona X

Colorado Desert 9. Clark Dry Lake X X X 10. Blair Valley X X II. Benson Dry Lake X X X 12. Mortero Wash X X X

BRSA' = Branchnecta sandiegoensis EUTE = Eulimnadia texana BRL1 B. lindahli EODI = Eocyzicus digueti STWO' = Streptocephalus woottoni CZCN = Czyicus californicus THPL = Thamnocephalus platyurus 1RNE = Triops newberryi _ , species endemic to California.

et al. 1990). It hatches at 15-35°C, and tolerates number of growth lines, number of spines on the telson) temperatures above 40°C (Hillyard and Vinegar 1972, could easily be a consequence of their size (c. califomicus Belk 1977a) and a wide range of pH values (Eng et al. up to 16mm. and C. elongatusup to 7 mm.). The species 1990). Our laboratory results suggest that it has a slower isa widespread Californiaendemicwitha range extending development time than some Branchinectids (> 3 weeks), from the Los Angeles Basin through the Central Coast but attains a much larger size (up to 30+ nun). Mountains and up the Central Valley (Wootton and The T platyurus sites in the Colorado Desert of San Mattox 1958) although it is not found in a large number Diego County represent the western extension of its of sites within that range. Eriksen and Brown (1980) range (Table 1, Fig. I). This species was found in field found the species at low salinities, but tolerant ofa wide collections simultaneously with T. newberryi and range of temperatures and salinities. Our field sampling Eulimnadia texana. It was also found in some of the same and laboratory rearings suggest that it hatches over a playas as B. lindahli but after fillings later in the year wide range of temperatures and is extremely long-lived. (Table I). Adults of these two species were not found North of Los Angeles, it is found in vernal pools after together in the field. winter rains, at times in association with Linderiella occidentalis, and Leptdurus packardi. Concnostraca (Clam Shrimp) OtayMesa is the only site where C. caltfomicuswzs Cyzicus califamicus Packard is considered here to fOW1d in San Diego County, and its only reponed be the senior synonym of Cyzicus elongatus Mattox, occurrence south ofLos Angeles. This suggests that the since the differences between the two species (e.g., species may have been more widely distributed along the 10 Branchiopod Drversrry : Simovich and Fugate TRANS. WEST. SECT. WILDL. soc. 28: 1992

Pacific Coast but that development in Los Angeles and The following species are known from areas Orange Counties probably destroyed intervening sites. immediately surrounding San Diego County and could In San Diego County, C. californicus wasfound with B. possibly be found in the county with increased sampling: sandiegoensis and S. woottoni (fable I). Branchinecta lynchi Eng, Belk and Eriksen, Riverside Eocyzicus digueti Richard is considered here to be County; Linderiella spp., Ri verside County; the senior synonym ofEocyzicus concavus Ma ckin since Streptocephalustexanus Packard, Riverside and Imperial the differences between the two species are, as in Cyzicus Counties; Triops long icaudatus Packard, Baja California likely to vary with size. This species is known from Norte, Mexico. Kansas south into central Mexico and west to southern California and Baja California (Mattox 1954 , Wootton CONCLUSIONS and Mattox 1958,Maeda-Martinez 1991). Almost nothing Theeight species found in San Diego County represent has been reported about the biology of this species, but it approximately 25% of the di verse branchiopod fauna appears to be found in desert playas (Sublette and found in California and an eight-fold increase over the Sublette 1967, Kubly 1982). In Anza Borrego playas, it number previously reported. The species are equally was found with B. lin dah li, T. platyurus and T. newberryi divided between the two biogeographic areas represented (Table 1). in San Diego County. Three ofthe species arefound only Eulimnadia texana Packard is widely distributed in in the South Coast Mountain region, four, only in the the southern U.S. west of the Mississippi, in central Colorado Desert region and only one species, B. /indah/i Mexico and in Baja California (Sassaman 1989, Maeda­ is found in both (Table 1). TIlls result corroborates the Martinez 1991). Little information has been published findings ofmany previous studies (prophet 1963 , Home on the biology of this species but it is capable of both 1967, Brach 1969, Belk and Cole 1975, Bernice 1972, bisexual and unisexual reproduction and sex ratios are Hartland-Rowe 1972, Belk 1977, Sam and Krishnaswamy almost always female-biased (Sassaman 1989) . Our 1979, Alonso 1985, Bowen et aI. 1985 , Bowen et al . laboratory results suggest that it prefers temperatures 1988, Brach 1989) and most recently Eng et al . (1990), above 20°C and reaches maturity quickly (withi n a few that the thermal and chemical properties ofwaterare two weeks) (unpubl. data). The species was found only in one ofthe mainfaetors determining branchiopod biodiversity. small desert pool at Mortero Wash with T. platyurus and A strong historical component also appears to be involved T. newberryi. Eulimnadia texana was not found in the in the biogeography of inland waters (e.g., Stebbins large desert playas that we sampled. 1976, Dumont 1980, Frey 1982, Belk 1984). For example, ofthe eightendemic speciesofAnostracans in California, Notostraca (Tadpole Shrimp) five (one undescribed) are found entirely or mostly in the Triops newberryi Packard is one of three species Central Valley, two only in extreme Southern California, described by Packard (1883) which were synonymized and the last is found only in Mono Lake (Eng et al . 1990, with Triops longicaudatus by Linder (1952) and Fugate and Belk unpubl. data). Longhurst (1955). Clear evidence exists from Our lack ofunderstanding as to precisely how these morpbological, electrophoreticandbiological differences physical, chemical and historical factors influence that T. longicaudatus consists of two species, T. branchiopod distributions may have led us to longicaudatus and T. newberryi (ms . in prep.). Triops underestimate the total diversity in the county, since our newberryi is found primarily in playas west of the sampling was exhaustive neither in time nor space. In continental divide while T. longicaudatus, is more the field, different species ma y appear in the same pools common east of the divide (Simovich et al . 1988, when they fill at different timesofthe year or a succession Sassaman 1991). The physiological requirements of T. ofspecies may appear overthe lifetimeofapool (Schafema longicaudatus have been the subject of several studies 1931ab, 1934; Relal1ack and Clifford 1980; Donald (Horne 1967, 1971; Hillyard and Vinegar 1972; Scott 1983; Thiery andGasc 1991 ; this study). In the laboratory and Grigarick 1979), but little is known about T. hatching may occur at water temperatures ranging from newberryi. Kubly (1982) reported physico-chemical 0° to 40°, but most species hatch over a more narrow data for southern California playas, some of which range (Nourisson 1964, Belk andBelk 1975, Belk 1977b, contain populations of T. newberryi (Sassaman 1991) . Simovich ms. in prep.) These results suggest that unless The species reproduces bisexually and unisexually and a pool is sampled several times over a year and over has a female-biased sex ratio similar to E. texana several years or hydrated in the laboratory over a wide (Sassaman 1991) . It was found in the Colorado Desert range of temperatures, species may be missed. of San Diego County with B. /indah/i in winter and with A better understanding of this problem is crucial T. platyurus, E. digueti and E. texana during summer because S. woottoni and B. sandiegoensts from San months (Table I) . Diego County, and all of the other California endemics TRANS. WEST. SECT. WILDL. SOc. 28:1992 Branchiopod Diversity· Simovich and Fugate II are threatened with extinction due to urban and eufilopodos no Cladoccros de la peninsula Iberica: agricultural expansion (Eng et al. 1990). San Diego observaciones de la morfologia cxtcrna mediante County has already lost 97% of its vernal pools (E. tecnicas de microscopia electronica de barrido. Bauder , pers . comm.) and many of those that remain Occologia aquatica 7:73-78. show signs of disturbance. It appears from this stud y that Balko, M. L., and T. A. Ebert. 1984 . Zooplankton disturbance may change species composition by allowing distribution in vernal pools of Kearny Mesa, San species not typically found in vernal pools (e.g., B. Diego, California. Pages 76-89 in S. Jain and P. Iindah/i) to colonize, and either hybridize with or replace Moyle, eds. Vernal pools and intermirtent streams. endemic species. Eriksen, Prettyman, and Moeur (1986) Univ. of Calif. Inst. of Eco!. Pub!. 28, Davis. also report that off-road vehicles, when driven on dry Bauder, E. T. 1986. San Diego Vernal Pools. Report to pools or playas , decrease the hatching of branchiopod California Fish and Game Endangered Plant Project. eggs by crushing them and compacting the soil. U.S. Fish and Wildlife Service Contract EP85Il-1. Furthermore, increased isolation ofpopulations in already Belk, D. 1975. Key to the Anostraca (fai ry shrimps) of fragmented habitat can have major effects on their North America. Southwestern Naturalist 20 :91­ genetic structureand resilience (Frankel and Soul e 1981, 103. Harris 1984). ___. 1977a. Evolution of egg size strategies in fairy The destruction of vernal pools and other similar shrimps. Southwestern Naturalist 22 :99-105. habitats threatens not only branchiopods, but many other ___. I 977b. Zoogeography of the Arizona fairy animal and plant species (Jain 1976, Herbst 1982, Jain shrimps (Crustacea: Anostraca). Journal of the and Moyle 1984, Jeffries 1991, Shoup 1991) . Our Arizona Academy of Science 12:70-78. understandingof the physiological requirementsand life _ __. 1984. Patterns in anostracan distribution. histories ofbranchiopods and vernal pool communities Pages 168-172 in S. Jain and P. Mo yle , eds. Vernal is extremely limited (Kerfoot and Lynch 1987). It is, pools and intermittent streams. Univ. ofCalif. InSI. therefore, essential that we ensure the survival ofthe few of Ecol. Publ. 28, Davis. pp. 168-172. remaining temporary pools and playas in San Diego ___. 1989. Identification ofspecies in the conchos­ County. tracan genus E u/imnadia by eggshell morphology. Journal of Crustacean Biology 9:115-125. ACKNOWLEDGEMENTS _ __, and M. S. Belk. 1975. Hatching temperatures We would like to thank Mike Wells , Clay Sassaman, and new distributional records for Caenestheriella John Kornmeyer, Stacie Hathaway, JeffGlaspy, Heather setosa (Crustacea, Conchostraca). Southwestern Lamberson, Catherine Guffey, Kim Caruso, Betsy Naturalist 20:409dJ I. Colman, Diolinda Parsick, Gary Bell, Mark Jorgensen, __-" and G. A. Cole . 1975 . Adaptational biology of Dave Hogan, John Ruddley, Fred Sproul, Howard Weir desert temporary pond inhabitants. Pages 207-226 and Gordon Pratt for their help. We would like to thank in N. F. Hadley, ed. Environmental physiology of Denton Belk, Larry Eng and Larry Serpa for reviewing desert organisms. Dowden, Hutchinson, and Ross , the manuscript. This research was supported by a Inc., Strousberg, Pennsylvania. Catherine Ordway Stewardship Award from The Nature ___, H. 1.Dumont, and N. Munuswarny, eds. 1991. Conservancy, administered in part by the San Diego Developments in hydrobiology: studies on large Natural History Museum and by a series ofUniversity of branchiopod biology and aquaculture. Kluwer Aca­ San Diego Faculty Research Grants. demic Publishers. Boston. 288pp. _ _ _ , and L. Serpa. 1992. First record of Bronchi­ necta campestris (Anostraca) from California and LITERATURE CiTED casual observations of males of Anemia clasping AhU. S. B. 1991. Factors affecting contributions of the females of Branchinecta. Journal of Crustacean tadpole shrimp Lepidurus packardi to its oversum­ Biology . 12:511-513 . mering egg reserves. Hydrobiologia 212 :137-143 . Bernice, R. 1972. Hatching and postembyronic develop­ Alexander, D. G. 1976. Ecological aspects of the ment ofStreptocephalus dichotomus Baird (Crusta­ temporary annual pool fauna. Pages 32-36 in S. cea : Anostraca), Hydrobiologia 40 :251-278. Jain, ed. Vernal pools, their ecology and conserva­ Bowen, S. T., E. A. Fogarino, K. N. Hitchner, G. L. tion . Univ. of Calif. Inst. of Ecol. Publ. 9, Davis . Dana. V. H. S. Chow, M. R. Buonocristiani, and J. Alonso, M. 1985. A survey of the Spanish Euphyl­ R. Carl. 1985 . Ecological isolation in Anemia: lopoda. 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