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provided by Aquatic Commons November 1994 NOTICIAS DE GALAPAGOS 15

NOTES ON THE STATUS OF TERRESTRIAL ARTHROPODS IN GALÁPNCOS

By: Léon Baert (Translation assisted by Heidi Snell and K. Thalia East)

Despite far outnumbering the terrestrial vertebrates na. Such information is also of interest to the Galápa- in species diversity and population numbers, com- gos National Park Service (GNPS) and to CDRS for paratively little is known about the terrestrial developing and implementing management policies invertebrates of the Galápagos Archipelago. Most and for studies offaunal changes occuring due to the publications about Galápagos fauna deal with the sys- ever increasing human population within the islands. tematics, phylogeny, physiology, ecology, ethology Linsley and Usinger (1966) compiled the first and preservation of native vertebrates for which the insect species list for Galápagos, enumerating some islands are famous. Much work has also been con- 618 species, treated in about 190 publications. The ducted on introduced birds and mammals. In contrast, list was derived fromresults of collecting campaigns terrestrial arthropods have been given little attention. of 21 multidisciplinary expeditions ever since Charles ln 1982, Friedman Köster, then director of the Darwins visitin 1835. In alater supplement, Linsley Charles Darwin Research Station (CDRS), asked in (191 I ) added another 265 species, treated in 1 1 8 pub- an annual report , 'How many species of introduced lications. These additions were principally the result insects and invading invertebrates are there in the of collecting efforts of the Galápagos International islands?'. At that time even the number of native Scientific Program of the Californian Academy of invertebrates in Galápagos was unknown. This real- Sciences in 1963-64 and the collecting campaign of ization prompted some important changes. Three Leleup (1965) in 1964-65. long-term studies on the systematics and evolution- With this initial list, the first task of the Belgian, ary ecology ofterrestrial arthropods in the archipelago Canadian andAustrian research groups was to com- were initiated. In 1982, K. Desender, J.P. Maelfait pile summaries of known data on terrestrial and I, from the Royal Belgian Institute of Natural invertebrates in Galápagos. A data base was con- Sciences in Brussels, began a study of Arachnids, structed, containing the following types of Carabid beetles and Isopods. In 1985, Stewart Peck information: and several of his colleagues from Carleton Univer- 1) Literature citations for all invertebrate species of sity, Canada, started a study of several arthropod the archipelago. groups, especially beetles. Also in 1985, Heinrich 2) Distribution information of each species within and Irene Schatz of the University of Innsbruck, and between islands as well as on the continent. Austria, commenced a study of Oribatoid mites and 3) Whethereach species is introduced, native or "erì- Tenebrionid beetles. All three projects continue to demic". this day and while the groups work independently, 4) Ecological data for each species, such as habitat they have coordinated their projects to complement preference, seasonality, elevational zonation, dis- one another. persal power, diet and host specificity. Before any serious ecological work on a arthro- All major islands and volcanoes have been at least pod group could be conducted in Galápagos it was roughly sampled by the scientists. Due to improved necessary to have an understanding of the diversity arthropod capturing techniques such as pitfall, mal- and population numbers of all species inhabiting the aise, flying interception and bait traps the teams were islands. This required extensive taxonomic research able to almost double the arthropod species list dur- to identify and describe the existing invertebrate fau- ing the 1980s (see Table 1). Even now a collection t6 NOTICIAS DE GALAPAGOS No.54

Table 1. Growing number of species for the most important terrestrial arthropod groups.

t966 1980 l99t

Insecta 618 883 t592 Scorpions 2 0 2 Pedipalpi 0 0 7 Solifugae 0 0 1 Pseudoscorpiones 0 0 16 Opiliones 0 0 I Araneae 70 81 152 Acari 38 0 192 Amphipoda 0 0 4 Isopoda 0 0 l1 Chilopoda 10 0 13 Diplopoda 2 0 9 Symphyla 0 0 1

made on any island or volcano can add a new species ing small and large scale allopatry,parapaty, allopa- to the list. Table 2 provides a detailed example of try with secondary contact of sister species, and how the total number of spider (Araneae) species allo-parapatry. The same is true for spiders (e.g. recorded in Galápagos has increased after each col- Maelfait &Baert,1986) and may be intrinsic to small lecting trip. arthropods. Due to the efforts of the teams, we have a fairly Another important group of invertebrates in good idea of the composition of some of the arthro- Galápagos is the cave dwelling Cryptozoa. Other pod groups in the archipelago and have been able to than some fossil remnants of a probably endemic rat, conduct ecological analyses of the data. For exam- the only animals found in caves are invertebrate rep- ple, we have been able to compare spider communities resentatives of Crustacea, Arachnida, Chilopoda, among the different vegetation zones of Santa Cruz Diplopoda and Insecta. Leleup (1965) pioneered a Island (Baert et al., 1991) and of the five volcanoes study of cave animals in Galápagos which is now on Isabela Island (Baert et aI., 7990). We have con- being followed up by S. Peck and his team (see Her- cludedthat species compositionof spiders is correlated nandez Pacheco et aI.,I992). Cryptozoic arthropo ds primarily with the altitudinal gradient and thus the are of special interest in studying the principals and vegetation zones. On Isabela spider communities are historical processess of animal geography. They are also influenced by the age of the volcanos as well as often considered archaic or relictual and as having an by the presence or absence of human settlements and exceedingly slow dispersal potential. Some Crypto- agriculture. zoans have adapted to an extreme and can be K. Desender has been investigating distribution morphologically characteized by reduced or absent patterns of Carabid beetles (Desender et aI.,l992a). eyes, a reduction of body pigmentation, often a thin- He has shown that the Carabid beetles have a wide ning of body cuticle, flightlessness in normally winged variety of distribution and speciation patterns includ- groups and an increased physiological sensitivity to November 1994 NOTICIAS DE GALAPAGOS t7

Table 2. Growing number of spider species.

Year Number of Total Number Collectin&Expedition Species Added of Species

1877 6 6

1 889 5 11 1902 t7 38 Hopkins-Stanford 1 898- 1 899 1924 5 43 Williams 1923 t930 6 49 Norwe gian Zo olo gical 19 25 r970 2I 70 Cal. Acad. Sci. and Leleup ('64-'65) t982 11 81 Various publications 1982 29 110 Baert and Maelfait 1985 2 172 H.and L Schatz (1991) 1985 Ja 115 Peck et al. 1986 7 t22 Baert, Maelfait and Desender (1989) 1988 4 126 Baert, Desender and Maelfait (1991) 1989 8 134 Peck et al. (1991) t99t 11 t45 Baert, Desender and Maelfait (1991) t99l 4 r49 Peck and Heraty a r992 J t52 Abedrabbo

dehydration. Peck (1990) lists 56 species ofeyeless long-legged Scytodes longipes, and all the beautiful and reduced-eyed arthropods, of which 4O are native jumping spiders around Puerto Ayora, Santa Cruz, or endemic and 16 have become well established since such as Hasarius adansonii, Menemerus bivittatus their probably inadvertent introduction by man. and Plexippus paykulli (Fig. 1). Theridion rufipes, which lives both indoors and out and is often found INTRODUCED ARTHROPODS under the plank beds of tourist boats, tends to be carried from island to island. Latrodectus geometricus which V/hile a large proportion of arthropod species in I have only found under wooden seats at the Canal de Galápagos certainly colonized the islands naturally, Itabaca (Santa Cruz Island) and in the town of Puerto itis obvious that anumberhave been introduced since Baquerizo Moreno (San Cristóbal lsland) is another the islands were discovered and inhabited by humans. example of an introduced man-dependent spider. Kramer (1984) stated that the problem of introduced The true number of introduced species is difficult invertebrates, many of which may be man-dependent to assess because few extensive studies of arthropod immigrants, had not yet been and needed to be tack- groups in Galápagos have been published. However, led. Part of the problem was that it is often difficult it is known that 13 out of 18 cockroach species (Peck to know whether a non-endemic species was intro- and Roth, 1992),7 out of 8 Diplopod species (Shear duced by man or immigrated naturally. No doubts and Peck, 1981) and 10 out of 13 Chilopod species exist in the case of man-dependent immigrants, ex- (Shear and Peck, 1992) have been introduced to the amples of which are the spiders Heteropodavenatoria, islands by man. which inhabits almost every house in Galápagos, the Introduced species can negatively affect existing 18 NOTICIAS DE GALAPAGOS No.54

rapid spread of the introduced fire ant Wasmannia

zuropunctata (Lubin, 1 984; 1 985). W. auropunctata was probably introduced to in- habited islands of Galápagos during the 1930s. In

I97 5 , it was discovered on an uninhabited island at a camping area used by scientists. W. auropunctata is a tiny ant which lives in small colonies containing several queens and has a high level of swarming ac- tivity by which it disperses easily over large areas. The ants are highly aggressive and do not tolerate other invertebrates in their immediate vicinity. Areas infested by them undergo the loss of many endemic and native invertebrate species. This is especially true in the transition zoîe on Santa Cruz where they are most abundant. However, since there was never a complete inventory of invertebrate species before theW. auropunctara invasion, the extent of their im- pact cannot be quantified. Few spider species are able to coexist with lV auropunctata. Inparts of the transition zone not heavily infested with the ants we Figure 1. Sketch of an introduced jumping spider, Plexippus paykulLi (Salticidae), by L. Baet. encountered 16 spider species, whereas in strongly infested areas of the zone we found only two tiny oonopid spiders and one ochyroceratid spider, all of ecosystems. Arthropods can be as devastating to plant which were possibly introduced with the ants. and animal communities as can vertebrates such as By the time people realized what kind of damage goats, pigs and rats. However, their influence on the was being caused by W auropunctata, it was too late; natural community also depends on the achieved whole areas \ryere literally covered with the ants and equilibrium state of the natural community. For ex- it is likely that we will never be able to eradicate the ample, species which can fill an empty niche or which species without inflicting serious damage to other are able to adapt to harsh conditions of a specific native invertebrates. microhabitat not occupied by a native species, can Introduced invertebrates are in general extremely evolve toplay abenign oreven abeneficial role in the difficultto eradicate once they have established them- ecosystem. On the other hand, in Galápagos, diffi- selves. Generally they are small, they hide in tiny culties of natural colonization in the islands have cracks and holes and are thus easily overlooked. They resulted in simpler arthropod assemblages than those can easily be transported from one island to another found on the continent. This in turn may have made by means of cargo ship or tourist or fishing boat. them more vulnerable to human-assisted introduc- Once on land they can as easily been transported by tion of aggressive species. man over the whole island. Many also have the abil- In l9l 2,at the Galápagos Science Conference held ity to fly and can colonize nearby islands on their in Washington DC, the continuation of "alpha level" own. Only one gravid female is needed to start an systematics for the diverse but still poorly known entire population, for invertebrates can breed at high invertebrate fauna in Galápagos was recommended. rates and inbreeding does not seem to effect popula- However, it was only in 1981 that the position of a tion quality. staff entomologist at the Charles Darwin Research Introduced invertebrates tend to be extremely dif- Station (CDRS) was established and that Dr. Yale ficult to eradicate in part because they are hard to Lubin was hired to study, among other things, the trace they are noiseless (or their sounds resemble November 1994 NOTICIAS DE GALAPAGOS t9

that of the native species and it takes an expert to tell auropunctata and P. versicolor, they do not sting and the difference), they don't leave footprints, they tend have not come directly into contact with humans. to disappear into places difficult to penetrate by man Only scientists working in Galápagos generally en- and they are not always very visible when flying. By counter them. But with these "hidden" introductions the time they become a nuisance they usually have too, native or endemic species may be adversely af- reached high population densities and are beginning fected. There are now two Cicindelidbeetles living in to disperse. By then it is too late to intervene without sympatry in lagoons and salt marshes along the coast drastic methods that may cause even more harm to of Santa Cruz (Desender et al.,l992b). One species, the native invertebrate fauna. Cicindela galapagoensis, is endemic andwell spread So, what eradication methods can be used? Each over the archipelago. The second species, Cicindela group or species requires a different eradication trifasciatct, is known from the western part of Central method. One possibility is biological control. For and SouthAmerica. Our data on C. trifasciata show this, a biological enemy is needed to control or erad- that it has only been collected since 1983, even though icate the pest species without becoming a nuisance the habitat it occupies on Santa Cruz has been searched species itself. This method opens new perspectives on many earlier occasions. The first individual was but needs a thorough initial study of the ecology of collected at the end of the 198211983 El Niño event. both the pest species and the biological control spe- Therecentpopulation growth andrelative abundance cies which is, of course, yet another introduced species of C. trifasciata in the Bahia Tortuga lagoon area and therefore a potential problem species. compared to that of the endemic C. galapagoensis An example of arecentintroduction is thePolisl¿s shows it has become very abundant in a short time versicolor wasp. This introduction apparently oc- span. The introduced species may be displacing the curred in 1988 during a shipment of bananas and endemic species. The restricted occunence of C. other fruit from mainland Ecuador to Floreana Is- trifosciata on Santa Cruz suggests that it was intro- land. The wasp has since spread over all of the duced by man. However, the importance of the El archipelago. Not only is the sting very painful and Niño events must be emphasized in this particular sometimes causes fever, but P versicolor may be colonization. El Niño events may increase the num- having a significant negative impact on the Galátpa- ber of possible colonizations, primarily by an increase gos ecosystem by competing with native fauna. From in vegetation rafts from the mainland forming and an unpublished report prepared by Jhon Heraty at al., reaching Galápagos due to increased rainfall on the the majorprey item of P versicolormightbe caterpil- mainland, but also because climatic conditions are lars, a major dietary item of many birds and reptiles more favorable for establishment of newly arrived and of Calosoma beetles. The danger exists that a species in the usually harsh environments of Galápa- severe disruption of caterpillars might have disas- gos. Such events may well have helped during the trous effects on these various populations. first steps in the adaptive radiation and evolution of Polistes wasps are not regarded on the mainland many invertebrates of the archipelago. as pest animals in normal numbers, but as an intro- A second hidden introduction involves the spider duced species on the remote islands of Galápagos Anyphaenoides octodentata. A. pacifica is wide- things may be different. For this reason the wasps are spread over the Galápagos archipelago, from the being observed closely and anxiously by entomolo- pampa down to the littoral zone. The vicinity around gists at CDRS under the supervision of Sandra CDRS is always emphasized during each collecting Abedrabbo, and eradication possibilities are being campaign. The second to last collection done in this discused. For exampl e, Polistes have many parasites area in 1989 by Peck revealed the presence of only (over 40 species are known) and one of them may the native species A. pacifica. Our last collections possibly be useful as a biological control agent. (by Peck and myself) in 1991 revealed the sudden Other recent introductions of exotic invertebrates presence of a second congeneric species,A. octoden- have not illicited much attention because unlike Wi tata (11 specimens) living sympatrically with the 20 NOTICIAS DE GALAPAGOS No.54

former species. This species has a wide continental human-introduced arthropods on the native fauna with distribution from Venezuela to Perú. a synopsis of a comparative study on the spider com- An interesting note about the species is that it was munity of different vegetation zones on Santa Cruz discovered for the first time in I91l in the German (B aert et al., 199 7). Our data rev eal 22 species for the seaport of Hamburg in a load of Ecuadorian bananas. agricultural zone (outside Park boundaries) and 20 Has this species been accidentally introduced to species for the remaining Scalesia arcanearLos Ge- Galápagos in a shipment of bananas or other fruit or melos. The transformation of the original Scalesia vegetables from the mainland? It certainly appears zone into the agricultural zone resulted in a slight so, asA. octodentata appeared suddenly in the vicin- quantitative enrichment (with only two additional ity of PuertoAyora where most of the goods shipped species), but also in a qualitative impoverishment of from the mainland to Santa Crtz are unloaded. A the original Scalesia fauna. For instance, seven en- specimen was also found atPuerto Baquerizo Moreno, demic species and two native species disappeared the shipping port for San Cristóbal. and were replaced by three endemic species originat- It seems clear that introductions are occurring ing from the lower arid zones, by one native species, through transport of goods by boat and by plane from four man-dependent species and by two introduced mainland Ecuador. Food products are especially likely species, the man-dependent and introduced species to carry unwanted invertebrates. The nonchalance obviously having a lower value for nature conserva- with which the unloading of merchandise is conduct- tion and the maintenance of biological diversity in ed indicates a need for more controlled supervision Galápagos. of docking activities. All goods should be carefully controlled and if necessary treated in an adequate LITERATURE CITED way to insure that no living animals are transported along with them. As long as there is no better control Baert, L., Maelfait, J.P. and Desender, K. 1989. of the the import goods to the islands there remains Results of the Belgian 1 986-expedition: Araneae, the very real danger of continuing to introduce poten- and provisional checklist of the spiders of the tially harmful plants and animals to the islands. Galápagos archipelago. Bulletin van het Konin- Tourism also plays a negative role in affects on the klijk Belgisch Instituut voor Natuurwetenschappen local fauna and flora. Boats travelling between is- Entomologie 58:29-54. lands increases the risk of genetic pollution between Baert, L., Maelfait, J.P. and Desendet, K. 1990. A the well established isolated populations of closely preliminary study of the spider communities of related taxa. Insects are frequently attracted to the Isla Isabela (Galápagos Archipelago, Ecuador). lights of tourist and fishing boats anchored near shore Bulletin de la Société européenne d'Arachnologie at night. Boats often travel between islands at night (N" hors série 1) 10-16. or in the predawn hours carrying these insects to a Baert, L., Desender, K. andMaelfait, J.P. 1991. Spi- new location. A recent study revealed that flying der communities of Isla Santa Cruz (Galápagos, insects are much less attracted to yellow light than Ecuador). Journal of Biogeography 18:333-340. white light. The use of yellow lights shouldbe oblig- Desender, K., Baert, L. and Maelfait, J.P. 1992a. atory on every boat navigating in the Galápagos Distribution and speciation of carabid beetles in waters. the Galápagos Archipelago (Ecuador). Bulletin Finally, man is not only affecting the faunal com- van het Koninklijk Belgisch Instituut voor Nat- position of the islands by introducing animals by uurwetenschappen: Entomologie 62:51 -65. design or accident, but also by altering the natural Desender, K., Baert, L. and Maelfait, J.P. 1992b. El landscape. One example is the exploitation of the Niño-events and the establishment of ground bee- mo st fertile zone of S an ta Cruz, the S c al e s i a zone, fot tles in the Galápagos Archipelago. Bulletin van agricultural activities and livestock. To end this ar- het Koninklijk Belgisch Instituut voor Natuur- ticle I give a specific example of the impact of wetenschappen: Entomologie 62:61 -1 4. November 1994 NOTICIAS DE GALAPAGOS 21

Hernandez Pacheco, J .J .,Zamora, I.I. and Masoliver, Peck, S.B. 1990. EyelessArthropods of the Galâpa- P.O. 1992. Carâlogo espeleológico de las Islas gos Islands, Ecuador: Composition and Origin of Galápagos. Resultados Cientificos del proyecto the Cryptozoic fauna of a Young, Tropical, Oce- Galápagos 2: ll-179. anic Archipelago. Biotropica 22(4): 366-38 1. Kramer, P. 1984. Man and other introduced organ- Peck, S.B. 1991. The GalápagosArchipelago, Ecua- isms. Biological Journal of the Linnean Society dor: With an Emphasis on Terrestrial Invertebrates, 2l:253-258. Especially Insects; and an Outline for Research. Leleup, N. 1965. Existence d'une faune cryptique Proceedings of the Forth International Congress relictuelle aux iles Galápagos. Noticias de Galápa- of Systematic and Evolutionary Biology (ed. gos 516:4-16. E.C.Dudley). Pp. 3 19-336. Linsley, E.G. 1971. Insects of the Galápagos (Sup- Peck, S. and Roth, L.M. 1992. Cockroaches of the plement). Occasional Papers of the California Galápagos Islands, Ecuador, with descriptions of Academy of Sciences 125:1-50. three new species (Insecta: Blattodea). Canadian Linsley, E.G. and Usinger, R.L. 1966. Insects of the Journal of Zoology 10:2202-2217. Galápagos Islands. Proceedings of the California Schatz, H. 1991. Catalogue of known species of Academy of Sciences 33(7 ):113-796. Acari from the Galápagos Islands (Ecuador, Pa- Lubin, Y.D . 1984. Changes in the native fauna of the cific Ocean). Intemational Journal of Acarology Galápagos Islands following invasion by the little 17(3):2t3-225.

red fire ant, Wa s manni a auro p unc t ara. B iolo gic al Shear,W.A. andPeck, S.B. 1987. Millipeds (Diplopo- Journal of the Linnean Society 2l:229-242. da) of the Galápagos Islands, Ecuador. Canadian Lubin, Y.D. 1985. Studies of the little fire ant,Was- Journal of Zoology 65:2640-2645.

mannia auropunctata, in a Niño year. in El Niño Shear, W.A. and Peck, S.B. 1 992. Centipeds (Chilopo- en las Islas Galápagos: El evento de 1982-1983. da) and Symphyla of the Galápagos Islands, Pp.473-493. Ecuador. Canadian Journal of Zoology lO:2260- Maelfait, J.P. and Baert, L. 1986. Observations sur 2214. les Lycosides des Iles Galápagos. Mémoire de la Léon Baert,Institut Royal Des Sciences Naturel- Société Royal Belge d'Entomologie 33: 139-142. les De Belgique, RueVautire29,B -1040 Brussels, Belgium.

K. Thalia East