Insect Conservation and Islands

248 Pages·2008·6.363 MB·English

by  Tim R. New

INSECT CONSERVATION AND ISLANDS
INSECT CONSERVATION AND ISLANDS
Editor
T. R. New
La Trobe University, Melbourne, Australia
Reprintedfrom Journalof Insect Conservation
Volume 12,Numbers 3–4(2008)
123
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Cover illustration: The cover illustration shows several examples of spectacular weta (Orthoptera) from New
Zealand, where their conservation has depended largely on offshore islands as refuges and introduction sites, as
discussed in papers in this publication. The insects can be fitted with harmonic radar transponders or micro-
transmitters for individual tracking. Shown are a Cook Strait Giant Weta, and two Mercury Island Tusked Weta
(photograph courtesy of Danny Thornburrow, Corinne Watts and Ian Stringer).
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Table of Contents
EDITORIAL
A special issue on insect conservation and islands
T.R.New 1
PAPERS
Insect conservation on islands: setting the scene and defining the needs
T.R.New 3–10
Butterflies of European islands: the implications of the geography and ecology of rarity and endemicity
for conservation
R.L.H.Dennis· L.Dapporto· T.G.Shreeve· E.John· J.G.Coutsis· O.Kudrna· K.Saarinen· N.Ryrholm·
W.R.Williams 11–42
Island size is not the only consideration. Ranking priorities for the conservation of butterflies on Italian
offshore islands
L.Dapporto· R.L.H.Dennis 43–55
A multidimensional characterization of rarity applied to the Aegean tenebrionid beetles
(Coleoptera Tenebrionidae)
S.Fattorini 57–69
The occurrence and distribution of carabid beetles (Carabidae) on islands in the Baltic Sea: a review
D.J.Kotze 71–82
Conservation of Southern Ocean Islands: invertebrates as exemplars
S.L.Chown· J.E.Lee· J.D.Shaw 83–97
Preliminary conservation status and needs of an oceanic island fauna: the case of Seychelles insects
J.Gerlach 99–111
Insect conservation in early succession on islands: lessons from Surtsey, Iceland, and the Krakatau
Archipelago, Indonesia
T.R.New 113–118
Issues and implications for research on disturbed oceanic islands illustrated through an ant survey of the
Cocos (Keeling) Islands
P.J.Neville· D.J.O’Dowd· A.L.Yen 119–129
Conservation status and needs of butterflies (Lepidoptera) on the Torres Strait Islands
D.P.A.Sands· T.R.New 131–138
Climate variability, biological control and an insect pest outbreak on Australia’s Coral Sea islets: lessons for
invertebrate conservation
P.Greenslade 139–148
Grasshopper outbreak challenges conservation status of a small Hawaiian Island
A.V.Latchininsky 149–163
History of weta (Orthoptera: Anostostomatidae) translocation in New Zealand: lessons learned, islands as
sanctuaries and the future
C.Watts· I.Stringer· G.Sherley· G.Gibbs· C.Green 165–176
Possible rescue from extinction: transfer of a rare New Zealand tusked weta to islands in the Mercury group
I.A.N.Stringer· R.Chappell 177–188
Population studies and conservation of Jamaica’s endangered swallowtail butterfly Papilio (Pterourus)homerus
E.Garraway· A.J.A.Bailey· B.E.Freeman· J.R.Parnell· T.C.Emmel 189–203
Notes on the biology, captive management and conservation status of the Lord Howe Island Stick Insect
(Dryococelus australis) (Phasmatodea)
P.Honan 205–219
Invasive species threats to native aquatic insect biodiversity and conservation measures in Hawai’i and
French Polynesia
R.A.Englund 221–234
Philosophical justifications for the extirpation of non-indigenous species: the case of the grasshopper
Schistocerca nitens(Orthoptera) on the Island of Nihoa, Hawaii
J.A.Lockwood· A.V.Latchininsky 235–251
JInsectConserv(2008)12:195
DOI10.1007/s10841-008-9165-2
EDITORIAL
A special issue on insect conservation and islands
T. R. New
Publishedonline:10April2008
(cid:1)SpringerScience+BusinessMediaB.V.2008
‘Islandenvironments’havelonghadspecialsignificancein Understanding the ecology of island insects and the pecu-
conservation,becausetheyimplyisolationand,oftenlinked liaritiesofislandfaunasisdemonstrated byseveralfurther
withthis,vulnerabilityofthespeciespresent.Inthisspecial papers dealing with Indonesia, and with the Indian Ocean
issue,anumberofthemesrelevanttothewellbeingofinsects islands.
onislandsarediscussed,andexamplesfrommanypartsof Conservation concerns focusing on individual island
theworlddisplayedtoattesttothecontinuingrelevanceand species are exemplified by papers on a spectacular Jamai-
interestofthisareaofdocumentingandconservinginsects. can butterfly and a possibly alien grasshopper in Hawai’i.
Conservation integrates with biogeography in elucidating Practical conservation of insects involves novel and
theunusualtaxonomicfeaturesofmanyislandinsects,and intensiveapproaches,suchastheuseofislandsaspredator-
the amount of basic information available on island insect free translocation sites for New Zealand weta, and an
faunasthroughouttheworldisextremelypatchy. innovative conservation breeding exercise on a notable
Following a general introductory essay to help ‘set the island endemic stick insect. A concluding paper discusses
scene’,thefirstgroupofpapersdealswithinsectsonsome some of the wider conceptual and philosophical issues on
ofthebest-documentedislands,thoseofEurope.Studieson recognition and values of island insect conservation.
selected insectgroupsonMediterranean andBalticislands I am very grateful to all participating authors for their
illustrate the relatively confident interpretations of faunal enthusiastic support of this special issue, and to the
affinity and conservation need that can be made in such numerous colleagues who have reviewed manuscripts,
well-studied cases. Each island and island group has indi- some at very short notice but always professionally and
vidual peculiarities and a review of the insects of southern perceptively. I hope the outcome will be a worthwhile
Atlantic Ocean islands demonstrates the more restricted window on some of the problems faced by island insects
and characteristic faunas at those more extreme latitudes. and how at least some of those problems are gradually
With the major exception of the Hawai’ian archipelago, coming to be better understood. Our Publishing Editor at
manyoftheislandsofthePacificregionaremuchlessfully Springer, Zuzana Bernhart, has continued to support this
documented, and a series of papers on islands within the enterprise enthusiastically, and much of the work of pre-
Australian region demonstrate both the difficulty of deter- paring the papers for publication has fallen to Pauline
mining which insects may be important conservation Lichtveld, whose exemplary professionalism has ensured
targets, and some of the pernicious threats that face them. the high production standard of this special issue.
T.R.New(&)
DepartmentofZoology,LaTrobeUniversity,
Victoria3086,Australia
e-mail:[email protected]
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JInsectConserv(2008)12:197–204
DOI10.1007/s10841-008-9159-0
ORIGINAL PAPER
Insect conservation on islands: setting the scene and defining
the needs
T. R. New
Received:18August2007/Accepted:15December2007/Publishedonline:27March2008
(cid:1)SpringerScience+BusinessMediaB.V.2008
Abstract The putative peculiarities of island insects and island or other narrow range endemism and of explosive
the factors important in their conservation are noted. radiations of species in isolated environments, the patterns
Endemism and speciation lessons from island insects have of invasion and faunal development, and development of
contributed significantly to wider understanding of aspects features such as flightlessness and unusual feeding habits
of insect diversification. The twin complexes of threats to (such as the predatory habit of Eupithecia caterpillars in
island insects involve (1) internal processes, essentially Hawai’i: Montgomery 1983) have been important compo-
habitat changes byhumanactivity,and their consequences nents of illuminating understanding of the natural world.
and (2) externally-imposed effects from alien invasive However, many island environments have also proven to
species, both of these operating in environments that may be highly vulnerable to anthropogenic changes and
lack much of the buffer capability present in larger conti- despoliation,invasionbyalien(exotic)organisms(manyof
nental areas or in richer communities. Many island insects them transported by people—even by scientists: Whinam
now persist only in small inaccessible remnant habitats, et al. 2005, noted the roles of expeditioners as vectors of
and protecting these is a key theme in planning insect exotic organisms to the remote subantarctic Macquarie
conservation on islands. The possible effects of climate Island), and wider exploitation. Patterns of insect distri-
changemaybesevere,particularlyon‘lowislands’suchas bution and speciation, and the taxa that have evolved on
many coral cays. islands continue to be changed, and species and commu-
nities to be lost. In this introduction, some of the major
Keywords Endemism (cid:1) Habitat loss (cid:1) Invasive species (cid:1) concerns about insect conservation on islands are exem-
Isolation (cid:1) Taxonomic radiation plified and discussed. Much additional information on
insect evolution on islands is included in the comprehen-
sive review by Gillespie and Roderick (2002).
Introduction
Insect faunas on islands have long held a particular fasci- Islands
nation for entomologists, biogeographers and evolutionary
biologists, in part because of the ‘romanticism’ of remote The very term ‘island’ implies isolation and, over the last
isolated environments but also because of the biological half century or so, ecologists have drawn many parallels
and evolutionary consequences of that isolation and, in between true islands in the oceans and fresh water, and
turn, the vulnerability of many of the environments habitats and resources distributed patchily in the wider
involved. The taxonomic novelties arising from single environment. Heterogeneity on all continents includes an
enormous mosaic array ofdifferent biotopes andresources
thatareseparatedspatiallyand,infunctionalterms,maybe
T.R.New(&)
just as isolated as more obviously defined islands. Thus,
DepartmentofZoology,LaTrobeUniversity,
Beaver(1967)referredtotheisolateddeadsnailssoughtby
Victoria3086,Australia
e-mail:[email protected] specialised carrion-feeding flies as ‘island habitats’, and
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Carlquist (1965) drew attention to the parallels between stages of the complex ecological processes of developing
isolated mountain tops and true islands. The many similar insectassemblages,Surtsey(Iceland)beingbyfarthemost
contexts include rarer isolated host plants of insect herbi- completely documented case (Fridriksson 1975) and mak-
vores as islands within multi species vegetation stands. ing for informative comparison with the Krakatau
Patterns of insect endemism on continents tend to reflect archipelago (Indonesia) (Thornton 1996, 2007).
‘island distributions’ on this scale of biotope or resource Manyislandsarefarolder.TheGala´pagos,forexample,
patchiness, and the vast majority of insect species that havebeencolonisedoversome3–4 millionyears,andtheir
attract individual conservation attention are restricted in vegetational and altitudinal complexity has facilitated
such ways—to some non-uniformly distributed specialised complex patterns of colonisation and speciation. Broad
resource or environment. Island biogeography theory patternsofinsectcolonisationofoceanicislandshavebeen
(particularly the seminal book by MacArthur and Wilson discussed by numerous authors. Thornton (2007) summa-
1967)hasbeencentraltopromotingunderstandingofsuch rised many of the attendant themes, and the difficulties of
systems, at any level of definition. As such, islands may interpretingcolonisationprocessesandtheirconsequences.
support isolated populations of species or constitute parts Insomecases,importantislandneoendemicradiationshave
of a geographical or functional archipelago subject to arisenfromsinglecolonisationeventsinthepast.Oneofthe
cyclic or more irregular colonisations and extinctions by better understood endemic radiations on the Hawaiian
supporting metapopulations of insects transcending more archipelago,forexample,isthedipteranfamilyDrosophil-
than one island (Hanski and Gilpin 1997). Very similar idae. It is estimated to contain around 1000 Hawaiian
conservation principles apply to island habitats within species,ofwhichabouthalfhavebeendescribedformally.
continentsandtothe‘trueislands’thatarethemajorfocus Molecular(DeSalle2001),behaviouralandmorphological
here, and many of the examples noted do indeed have data (Kaneshiro et al. 2001) collectively help to elucidate
continental counterparts and parallels. As Gillespie and their evolutionary relationships, to demonstrate their
Roderick (2002, p. 597) put it ‘ … the perception of an monophylyandtherestricteddistributionsofmostspecies,
isolated habitat as an island depends on the organism in andtoillustratethepatternofsubsequentcolonisationsalong
question’. theislandchainfromoldertoyoungerislands.AsFunkand
This special issue deals predominantly with ‘proper Wagner(2001)noted,thisarchipelagopresentsevolutionary
islands’—with oceanic or continental land entities and the biologists with a ‘conveyor belt’ as islands drift progres-
insects they harbour in their terrestrial and freshwater sively away from the hotspot from which they are formed,
environments. Continental islands are typically dominated withacommonpictureofthemostancestralspeciesonold
by insects representative of those on nearby larger land islandsandmostderivedspeciesontheyoungerones.
masses, often as a ‘subset’ of those but, depending on the However, rates of insect introductions to islands are
extent of isolation, speciation to varying extents from difficult to assess, not least because of lack of long term
remnant resident taxa (palaeoendemics) is common. If documentationandthedifficultiesofrecordingtheirinitial
repeatedorcontinuedcolonisationsareneededtoreplenish presence. The pattern of winged insect introductions and
the island fauna, conservation considerations must then establishmentontheremoteGoughIsland(SouthAtlantic)
extend also to the continental source areas. Continental was discussed by Gaston et al. (2003). Of 99 species then
islandinsectdiversitytendstodecreaseovertimefromthat recorded on the island, 71 are established introductions,
of the parental environment, but this depends also on dis- and 28 indigenous. The introduced species represent a
tance from sources. Many islands might, conversely, show putativeestablishment rate ofaround oneineverythree or
increases—such as in response to build up of fauna on four landings by people, suggesting substantial compati-
source areas due to range changes. Oceanic island insect bility of the receiving environment and low ‘biotic
assemblages reflect the processes emanating from insect resistance’. If the number of founders is small, some form
arrivalsandsubsequentevents,with(commonly)theirhigh ofgeneticbottleneckmaybeanimportantinfluenceonthe
levels of isolation and initial low diversity environments evolutionary future of the ensuing population (Carson
sometimes fostering high levels of endemism (such as in 1992, on Krakatau).
the Gala´pagos and Hawai’i) to produce diverse arrays of
island or archipelago endemics of global evolutionary
significance. These categories are broadly paralleled in Insects on islands
Gillespie and Roderick’s distinction between ‘fragment
islands’(anyhabitatthathasbrokenofffromlargerhabitat Much of the concern for conservation of insects (and
andbecomeseparatedbyanexpanseofunlikematrix)and other biota) on islands flows directly from their isolation
‘Darwinianislands’(anynewlycreatedhabitatthatappears and individual peculiarity and irreplaceability. Loss of
withinanunlikematrix).Averyfewcasesrevealtheinitial endemic species per se is clearly important, but the wider
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JInsectConserv(2008)12:197–204 199
implication is that their loss disrupts or destroys the in Hawaii, together with around 15% of extant families.
patterns needed to interpret the evolution of complex The10,000orsoendemicinsectspeciesonthearchipelago
island faunas. (references in Howarth and Ramsay1991) represent radia-
On oceanic archipelagoes, many insect species are tions from a very limited subset of potential colonists.
restricted to single islands, so that taxonomic isolation Clearly,theprecisespectrumofsuccessfulcolonistsonany
manifests at the twin scales of island and archipelago. island reflects considerable chance but, for example, aeo-
Where the age relationships between different islands is lian insect communities in widely separated parts of the
understood, as in Hawai’i, with different islands in the world may exhibit considerable common elements
chain ranging from about 0.5 million years (Hawai’i) to (Thornton 2007), with early assemblages on bare lava in
around30 millionyearsold(KureAtoll,some2500 kmto Hawai’i, Indonesia and the Canary Islands broadly rather
the west) (Howarth and Ramsay 1991), the patterns of similar in composition.
transitionbetweentaxamaybeevidentfromrecentfaunas.
Thus, drawing from Zimmerman (1948), Gagne´ (1997)
noted that there are probably more than 1000 species of Conservation need
endemic Hemiptera in Hawai’i, with many exhibiting ‘a
high degree of host or ecosystem specificity’, but also Habitat isolation and fragmentation in many terrestrial
(Gagne´ 1997, p. 6) that ‘Many Hawaiian Heteroptera now ecosystems (processes equivalent to the creation of conti-
occur in unstable environments that are threatened with nental islands) have many parallels with indicating
extinction’ with many of their host plants now virtually conservationneedsontrueislands,andconservationneeds
extinct.Usingthe50speciesofNesiomiris(Miridae)asan and priorities may be very similar. The greater inhospit-
example, Gagne´ noted that only 6 occurred on more than ability to many insects of ocean over land, however
oneisland,andonlytwospeciesoccurredonthreeislands. changed that land may be, may act as a further filter to
Fortyfourofthespeciesarealsomonophagousoneithera successful colonisation. As emphasised by MacArthur and
singlehostplantspecies(41)oronspecieswithinthesame Wilson(1967),andrestatedmanytimessince,boththesize
section or genus (3). of an island and its degree of isolation (measured most
Another Hawaiian endemic mirid genus, Savona, conventionallyasdistancefromsourcesforrecolonisation)
includes 40 species (Asquith 2001), many of them sepa- are important considerations in colonisation or replenish-
rated most easily by details of male genitalia. Savona has mentofislandbiotas,andoftherichnessthatanyparticular
radiated to exploit 17 genera of host plants in 14 families, island may sustain. On small habitat patches, as small
and also demonstrates progressive colonisation from older islands, extinction of a population may be equivalent to
to younger islands, accompanied by host-mediated speci- extinction of the species (see Levins 1970).
ation in areas of colonisation. All but one species of The development of insect conservation includes many
Savonaaresingleislandendemics,manyofthemrestricted examples of the former, small habitat patches, approach
to particular high volcanoes on an island. The general appliedtocontinentaltaxa.However,someputativespecies
patternofsingleislandendemismiscommonamongmany extinctions onislands have also causedconcern.
insect groups in Hawai’i. One, the Lord Howe Island stick insect (Dryococelus
For radiations of phytophagous insects such as the australis), was believed to have been exterminated by rats
above, thetwinlevelsofisolationonsingleislandsandon buthasrecentlybeenre-discoveredinsmallnumbersonthe
particularhostplants(as‘evolutionaryislandsintime’:see remote Balls Pyramid (Priddel et al. 2003; Honan this
Opler 1974, on Quercus foliage-mining Lepidoptera in volume). Another, the St Helena earwig (Labidura hercu-
California) help to indicate the reasons for their vulnera- leana,notableastheworld’slargestearwig),appearstobe
bility, as reflecting limited place of occurrence and extent trulyextinct.ItwasendemictoStHelena,andwascollected
of ecological specialisation. As elsewhere, insect conser- there by a Belgian expedition in 1965–1967, but more
vationinvolvesplantconservation,withwidespreadlossof recent searches have not found it. However, as is common
indigenous vegetation of major concern on numerous with insects, confirming extinction is in itself difficult.
islands and island groups. Many island plants rely on Several Hawaiian earwigs, likewise, are known only from
specific insect pollinators, which may have declined from oldmuseumspecimens.Again,however,manycontinental
human interference, particularly that related toagriculture, extinctionsinvolve such narrow range endemicsand many
with consequent cascade effects. current insect conservationconcerns involve such species
Radiations of species, such as those noted above, may Howarth and Ramsay (1991) opened their comprehen-
mask a degree of higher level faunal imbalance, in that siveessayonislandinsectconservationwiththestatement
many island insect faunas are depauperate at order level. ‘Toassessthestatusofislandinsectsandtheirhabitatsisa
Thus, only about half the orders of insects are represented daunting task’. However, there is wide agreement that
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