Peck, Stewart B.

English

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March1996 NOTICIAS DE GALAPAGOS
LITERATURE CITED
Broeker, W.S. 1989. The role of ocean-atmosphere reorganiza-
tions in glacial cycles. Ceochimica et Cosmochimica Acta
53:2465-250L.
Christie, D.M., Duncan, R.4., McBirney,4.R., Richards, M.4.,
White, W.M., Harpp, K.S., and Fox, C.G. 1991. Drowned
islands downstream from the Galapagos hotspot imply
extended speciation times. Natur e 355: 246-248.
Crisp (1984. Rates of magma emplacement and volcanic out-
put. |ournal of Volcanology and Geothermal Research 20:
177-217.
Defense Mapping Agency Hydrographic /Topographic Cen-
ter. 197 6. 22S4T,EashernApproach to Canal de San Salvador.
Washington, D.C.
Duncan, R.A. and Hargraves, R.B. 1984. Plate tectonic evolu-
tion of the Caribbean region in the mantle reference frame.
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Epp, D. 1984. Implications of volcano and swell heights for
thinning of the lithosphere by hotspots. Journal of Geo-
physical Research 89 : 9991-999 6.
Fairbanks, R.C. 1989. A17,000 - year glacio-eustatic sea level
record: influence of glacial melting rates on the Younger
Dryas event and deep-ocean circulation. Nature 342:.637-
642.
Feighner, M.A. and Richards, M.A. 1994. Lithospheric struc-
ture and compensation mechanisms of the Galápagos
Archipelago. Journal of Geophysical Research 99: 6711-
6729.
Geist, D.j., McBirney,4,R., and Duncan, R.A. 1986. Geology
and petrogenesis of lavas from San Cristobal Island, Gal-
apagos Archipelago. Geological Society of America Bulletin
97:555-566.
Geist, D, Howard, K.4., Jellinek,4.M., and Rayder, S. 1994, The
volcanic history of Volcán Alcedo, Galápagos Archipelago: A
case study of rhyolitic oceanic volcanism. Bulletin of Volca-
nology 56:243-260.
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relative to the hotspots incorporating the NUVEL-1 global
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1112.
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imación a la Isla Seymour e Isla Baltra. Guayaquil, Ecuador
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of the Galapagos Islands. Geological Society of America
Memoir 118.
Oerlemans, I. 1989. A projection of future sea level change.
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Reynolds, R., Geist, D, and Kurz, M. 1995. The volcanic devel-
opment of Sierra Negra volcano, Isabeia Island, Galápagos
Archipelago. Geological Society of America Bulletin: inpress.
Reynolds, R. 1994. Geology and petrology of Sierra Negra vol-
cano, Isabela Island, Galapagos Archipelago. Ph.D. Thesis,
University of Idaho.
White, W.M., McBirney, 4.R., and Duncan, R.A. 1993. Petrology
and geochemistryof the Galápagoslslands: Portraitof apatho-
logical mantle plume. Journal of Geophysical Research 98:
19æ3-19563.
Dennis Geist, Department of Geology and Geological
Engineering, University of ldaho, Moscow ID 838 44,USA,
Dgeist@uidaho.edu.
THE ARTHROPODS OF THE ALLOBIOSPHERE (BARREN LAVA
FLOWS) OF THE GALAPAGOS ISIANDS, ECUADOR
By, Stewart B. Peck
INTRODUCTION
Hutchinson (1965) proposed the term allobiosphere
to encompass habitats where photosynthesis is absent
because of environmental extremes, and life is support-
ed only by imported food materials. Examples are the
animal communities of caves, the ocean depths (Edwards
1988), and above the snow-line onmountains (Edwards
1987). The word is based on the Greek " allo" , meaning
different or of another kind, suggesting that these habi-
tats are not operating as parts of the normal biosphere.
Of interest to us here are young and barren lava flows
that have not yet been colonizedby plants.
Howarth (1979) was the first to recognize that recent
lava flows in the Hawaiian Islands are rapidly colonized
by arthropods within months after they have cooled, and
long before the appearance of macroscopic plants. The
animals scavenge on the wind-born (aeolian) fall-out of
organic debris (Swan 1992). T}:re lava flows are barren,
xeric, windy, and subject to both high insolation and large
daily temperature fluctuations (Howarth 1987). The ani-
mals usually are nocturnal foragers and they retreat to
deep cracks and crevices in the daytime. They may feed as
generalized scavengers but some species may also be re-
markably specialized and restricted to such habitats.
Since the work of Howarth on Hawaiian lava flows,
allobiosphere arthropod communities have been found to
10 NOTICIAS DE GALAPAGOS No.56
Table 1. Data for arthropod bottle traps in lava flows on the Galápagos Islands.
Young Barren Lava Flows
Sample Island Lava Flow Location Dates Elevation LifeZone
9r-140
92-22
92-35
92-99
92-704
92-30
92-57
92-74
92-89
92-113
Fernandina
Marchena
Pinta
Santiago
Santiago
May 3-10
March 11-24
March 13-21
Aprll4-1.4
April6-13
l|¡4arct.12-24
March 10-25
March 6-30
Aprlll-17
AprlIT-13
sealevel
sealevel
sealevel
5m
200 m
sealevel
5m
10m
30m
550 m
arid
arid
arid
arid
transition
arid
arid
arid
arid
humid
Older Forested Lava Flows
Marchena
Genovesa
Santa Cruz
Santa Cruz
Santiago
CaboHammond
Punta Espejo
Playa lbbetson
Playa Espumilla
Espumilla to Aguacate
SW Playa
Bahia Darwin
Darwin Research Station
Darwin Research Station
Aguacate Camp
exist in recent lava flows of the Canary Islands (Ashmole
andAshmole 1988, Ashmole et al. 1990,1992;Martinet al.
1987,7990) and Anak Krakatau Island, Indonesia (New
and Thornton 1988). These workers found that lava-flow
arthropods are most successfully collectedbybaited traps.
I thought it of interest to apply similar sampling tech-
niques to see if such a fauna exists on young and barren
lava flows of the Galapagos Islands, Ecuador.
METHODS AND MATERIALS
Trapping stations were placed in both young and old
pahoehoe lava flows on the Galapagos islands of Feman-
dina, Genovesa, Marchena, Pinta, Santa Cruz, an:.d
Santiago. The ages of the young lava flows are not known
but they have not been appreciably weathered and are
not colonized by macroscopic vegetation. On each flow
a total of 10 trap stations was set for a period of at least 7
days. The traps were set at least 4 meters apart, depend-
ing on the terrain. For comparison we also set traps on
older, weathered, vegetated lava flows.
The trapping procedure was similar to that employed
byAshmole and Ashmole (1988) and Ashmole et al. (1990,
7992). The traps were 250 ml disposable glass or plastic
bottles with about 50 ml of Turquin's liquid (which both
attracts and preserves arthropods) and a bait of 5 cc of
Danish blue cheese. Traps were placed as deep as possi-
ble into crevices in the lava, and set at a 45" angle. Small
rocks were placed around the tops to ensure easy access
for crawling animals. A modified formula of Turquin's
liquid was made from 15 g chloral hydrate, 20 ml concen-
trated formalin (40% formaldehyde), 10 ml glacial acetic
acid, 1 ml liquid dish-washing detergent and beer added
to make 1 liter of fluid. Turquin (1973) used only 5 ml of
formalin, 10 g of chloral hydrate, 5 ml of glacial acetic
acid,7 L of beer, and no detergent. I found that this older
formulation has less capacity to preserve the captured
arthropods. Turquin fluid itself is a bait as well as a pre-
servative. It attracts a wider diversity of fauna than an
exclusively formalin- or a vinegar-based preservative flu-
id (Borges 1992).
In addition to trapping we made visual searches for
arthropods around the first station at each site: 15 min-
utes were spent turning over rocks and 45 minutes
searching on the surface and in accessible crevices.
The data for trap locations are in Table 1.
RESULTS
No fauna was fould in the daytime visual searches in
the new lava flows. This serves to reinforce the general
observation that young lava flows are barren of life.
The results of the trap catches are in Table 2. A some-
what higher diversity and much larger number of
specimens were caught in the old and vegetated lava flows
than in young and barren flows.
The catch numbers have notbeen adjusted for the dif-
ferent periods of time the traps were operating. The fauna
caught on the barren flows are mostly wide-ranging
winged species. No distinctive species were found which
seem to be specialized to life in or on young lava flows.
The cricket Gryllodes sigillatus, which is an introduced
species, was fould on Santiago, Pinta, and Marchena for
the first time. It has not been reported in the literature,
and was previously otherwise known to me only from
CDRS, Isla SarrtaCruz, and Bahía Dant'in, Isla Genovesa.
At present, this species seems to be limited to coastal ar-
eas of the arid zone, and is not moving into interior habitats.
DISCUSSION
An adequate sample is not yet available from young
and barren lava flows to definitely determine if they have
a distinctive and specialized fauna as is known for the
i|lIarcll.1996 NOTICIAS DE GALAPAGOS 11
Table 2. Fauna captured in bottle traps place in lava flows of the Galápagos Islands.
Gastropoda 8
Young Barren Lava Flows
Fer,1 Mar. Pin. San. San.
1402 22 35 99 t04
1
11 13
1.
18
328
Old Vegetated Lava Flows
Mar. Gen. S. Cz, S.Cz. San.
30 57 74 89 113
Crustacea; Decapoda, Brachyura (crab)
Isopoda, Oniscoidea
Aranea
Acai;GøIumnasp.
Gamesina
Austrocørabodes sp.
S ac culob at e s " t enuipil o su s"
Diplopoda
Chilopoda, Scolopendra galapagoensis
Hexapoda, Collembola
Insecta
Thysanura, Lepismatidae
18 7 200
21
200
226
25
72053
11
41
2391644
49 23
1
12
3
1
1
3
611
1
1
12
825 3
1
t6
4
1
Orthoptera, Gryllidae, Gryllodes sigillatus 90 179 6
Hygronemobius sp. 5
Blattodea, Blatellidae, Symploce pøllens
Blattid ae, Pe ripln ne t n nme r icana
Hemiptera
Lygaeidae
Althocoridae
Miridae
Homoptera, Acanaloniidae
Cicadellidae
Delphacidae
Psyllidae
Psocoptera
Thysanoptera
Coleoptera, Carabidae, Pterostichus sp.
Histeridae, Euspilotus sp.
Hydrophilid ae, O osternum cost atum
Staphylinidae
Ptiliidae
Scarabaeidae, Ataenius ørrozui
Dermestidae
Nitidulidae, Stelidota insularis
Acribus sp.
Urophorus humeralis
Tenebrionidae
Ammophorus sp.
Stomion sp.
Chrysomelidae, Docema sp.
Bruchidae, Scutobruchus sp.
Scolytidae, Xyleborus ferrugineus
X. spinulosus
Hyp othenemus cylin dr i cus
Platypodidae, Plntypus santøcrucensis
Lepidoptera (moths)
Diptera, Muscidae
other families
Hymenoptera, Formicidae
Solenopsis sp.
Tapinoma sp.
Paratrichina sp.
W asmannia aur op unct øt &
Pheidole sp.
Campanotus sp.
Crematogaster sp.
Monomorium sp.
Microhymenoptera
Totals
311135
827
5 255
52
7 196
22
2 104
{
1
451 462 1.312
19
2776
41 19
17
2
22
292
1
9
31
1
3
95
3
1
159
5
48 174
59
4
2
1
2L
833 336
43
20198t4146
1
134
1
454
1 Islands: Fer. = Fernandina, Mar. = Marchena, Pin. = Pinta, San. = Santiago, Gen. = Genovesa, S. Cz. = Santa Cruz.
2 Collection sites, see Table 1 for descriptions.
12 NOTICIAS DE GALAPAGOS No.56
Canary Islands and Hawaii. On those islands it is known
that the distinctive fauna vanishes as biotic succession
proceeds, and that some of the specialized fauna ispresent
only near the sea coast. In both those island groups a
more diverse far-rna also occurs on new lava flows at high-
er elevations, where there is more wind-borne detritus as
a base to the food chain.
If this allobiosphere sampling program can be contin-
ued, especially on other islands, it will be possible to state
more conclusively whether or not a specialized pioneer
fauna exists on or in new lava flows. Then it will also be
possible to analyze the makeup of the faur.a, from the
viewpoint of detritivores and predators. At some sites
the biomass of the predaceous centipede Scolopendra ex-
ceeded the biomass of all the rest of the catches combined.
The other notable predators are the anthocorid bugs, the
Pterostichus carabids and the Euspilotus histerids. The
Euspilotus came from a very large population which was
feeding on fly larvae in dead sea-birds in a nearby colony
on Isla Genovesa. The scavenger arthropods themselves
are all broadly-feeding generalists. The Hemiptera (not
Anthocoridae) and Homoptera are probably phytophag-
es. They were more abundant on the forested lava flows.
Their attraction to the traps is not understood, but most
may be aerial waifs and part of the food supply rather
than members of the community.
In addition to an aeolian source of organic detritus in
the young lava flows, there may be a sea-borne source of
debris and food. This idea is supported by the fact that
some of the specialist faula of new lava flows in the Ha-
waiian and Canary Islands is found only in coastal areas,
and not far inland. We found that there is only a general
decline in numbers of individuals and of species away
from the coast.
ACKNOWLEDGMENTS
The samples reported here were gathered with the
assistance of student volunteers Maria-Teresa Lasso and
Elvia Moraima Inca. A scientific research permit was is-
sued by Galapagos National Park Service, A. Izurieta,
Superintendent. Field research logistics was arranged by
the Charles Darwin Research Station, C. Blanton and D.
Evans, Directors, Isla SantaCruz. TAME airlines of Ecua-
dor provided travel at a reduced rate. Research was
supported by an operating grant from the Canadian Nat-
ural Sciences and Engineering Research Council. Joyce
Cook aided with the sorting and identification of the in-
sects. H. Schatz provided identifications of the Acari. F.
Flowarth, P. Oromi, and P. Ashmole are thanked for
making constructive comments on this paper.
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on Hawaii Island: an ecosystem supported by windborne
debris. Pacific Ins. 20: 133-1,44.
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terranean habitats in Hawaii. Trends Res. Ecol. Evol. 2:
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Hutchinson, G.E. 1965. The ecological theater and the evolu-
tionary play. Yale University Press. 139 pp.
Martin, j.L. and P. Oromi. 1990. Fauna invertebrada de las lavas
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ias). Ecologia 4: 297 -312.
Martin, |.L. P. Oromi and I. Izquierdo. 1987. El ecosistema eolico
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(Islas Canarias). Vieraea 17 : 26L-270.
New, T.R. and I.W.B. Thornton. 1988. A pre-vegetation popula-
tion of crickets subsisting on allochthonous aeolian debris
on Anak Krakatau. Phil. Trans. R. Soc. Lond. 8322:481.-485.
Swan, L.W. 1992.TLre aeolian biomei ecosystems of the earth's
extremes. Bioscience 42: 262-270.
Stewart B. Peck, Department of Biology, Carleton Uni-
versity, Ottawa, Canada. KlS 586.


The arthropods of the allobiosphere (barren lava flows) of the Galapagos Islands, Ecuador

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The arthropods of the allobiosphere (barren lava flows) of the Galapagos Islands, Ecuador

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