Table Of ContentSelbyana 26(1,2): 299-303. 2005.
WHAT HAVE HERBARIA EVER DONE FOR US? THE ROLE OF
HERBARIA IN CONSERVATION ASSESSMENTS
DAVID L. ROBERTS* AND JUSTIN MOAT
Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, UK.
Email: [email protected]
GREG McINERNY
School of Biological Sciences, University of East Anglia, Norwich, Norfolk, NR4 7TJ, UK.
ABSTRACT. The world is entering a time of immense environmental upheaval, where experts increasingly
are required to provide conservation assessments. A quantitative assessment of trends in range and abun
dance of flora is costly, requiring extensive field studies over a long period of time. Unfortunately, many
plant species are known only from a few chance sightings or a handful of specimens. Specimen-based
records provide information on the distribution of taxa through time and space, and a wealth of this
knowledge can be found in the taxonomic collections and libraries of herbaria and museums. Conservation
assessments are increasingly important, as lists of threatened species often form the primary source of
information in the allocation of limited resources for conservation. One of the strengths of using herbarium
data is that the results are built on current taxonomic expertise. Such data are derived directly from indi
vidual, verifiable records, which represent primary observations. Here we describe a number of techniques
that are available for conservation assessments, including Red Listing of species.
Key words: extinction, decline, threat, herbarium data, conservation assessments, mCN Red List criteria
INTRODUCTION range and abundance is costly, requiring exten
sive field studies over a long period of time
Herbaria and other natural history collections (Burgman et al. 2000). The vast majority of spe
often have been considered mainly the realm of cies, however, are only known from a handful
taxonomic research, i.e., naming new species, of collections; thus these species often are ex
revisions, monographs, checklists, and floras. cluded from conservation assessments; or at
Such collections, however, have a lot more to best, they are recorded as data deficient due to
offer. Recent research has included the study of lack of information (McInerny et al. unpubl.
phenological response to climate change, confir data). If we cannot successfully monitor popu
mation of the existence of diseases in rodent lations for the purpose of conservation assess
populations prior to the outbreak in humans, ments, it becomes nearly impossible to predict
changes in population structure and genetic di their decline or extinction with any certainty.
versity caused by habitat loss, and estimation of Without such fieldwork, the status of a species
historical levels of environmental contaminants
may only be inferred from the information con
to provide a baseline for comparison with cur
tained within the specimen-based collections
rent levels (Graham et al. 2004, Suarez & Tsut (Mcinerny et al. unpubl. data); and such collec
sui 2004). The contributions of these institutes,
tions are estimated to contain ca. 2.5 billion
however, have gone largely unnoticed by the
specimens (Suarez & Tsutsui 2004). These re
public and the policymakers. This wide under
cords provide not only information on the dis
appreciation has resulted in insufficient financial
tribution of taxa through time, and space (Pon
support for maintenance and improvement of bi
der et al. 2001); they also represent primary ver
ological collections (Suarez & Tsutsui 2004).
ifiable observations and are built directly on cur
Threatened species lists are fundamental in
rent taxonomic expertise (Bachman et al. 2004).
providing a global context for biodiversity de
Even in cases where species are from well-stud
generation (Hilton-Taylor 2000); and they are
ied groups, extinction and rediscovery raises
the primary source of information for the allo
concerns about how we know when a species is
cation of limited resources for conservation
extinct, given the difficulty of effectively sur
(Burgman 2002). Such information is a frequent
veying and monitoring critically endangered
requirement in legislation (Mace & Lande
species. According to Mcinerny et al. (unpubl.
1991). Quantitative assessment of trends in
data), "Extinctions are most frequently asserted
after subsequent investigation, and so uncertain
* Corresponding author. ty often surrounds the classification of a species
299
300 SELBYANA Volume 26(1,2) 2005
T
I
1
••
~ ,
II ,
•
~--------------v------------_/
O<t<tn
FIGURE 1. The Solow equation evaluates the probability that n observations occurred before the last sighting
during the period t7•
as extinct. This necessitates acknowledgment of binary record, with multiple sightings recorded
the probabilistic nature of any extinction state as a single sighting for any single time unit; as
ment." Making false extinction claims could un the methods assume collections are independent
dermine potential last-minute conservation ac of one another (McCarthy 1998). The sightings
tion; and wider public support also could be un occur within the entire period, T, at ordered
dermined by conservationists "crying wolf" too times, t\ < t2 < ... < tn (FIGURE 1). Higher
frequently. probability values (>a) infer, therefore, that ex
For the purpose of conservation assessments, tinction has not occurred, as the lack of sightings
we are mainly interested in trends in abundance at the end of the record could happen by chance.
and range. Natural history collections contain Low probabilities «a) infer that extinction has
two main types of useful information for this occurred, as the sightings are unlikely to have
purpose, the time and the place of collection
occurred in the time period 0 ::,; t ::,; tn given the
(Le., the collection event, Suarez & Tsutsui
magnitude of T, and/or n.
2004). In some cases, other ecological infor
Increasing magnitude of p-values implies de
mation also is available. Firstly, the date of col
creasing levels of threat (McCarthy 1998). This
lections may be arranged as a binary record, as
also allows us to prioritize conservation effort
a time series. Several methods have been pre
by ranking the p-values generated. In addition,
sented that provide a probabilistic basis for the
if species were collected randomly and were not
extinction hypothesis based on such time series
in decline, then one would expect uniform dis
(Solow 1993a, 1993b; Burgman 1995; McCar
tribution; for example, species that are presumed
thy 1998; Solow & Roberts 2003; McInerny et
extinct would have the lowest p-values (McCar
al. unpubl. data). Essentially these methods pro
vide the probability that another collection will thy 1998).
be made given the characteristics of a time series Several methods have been developed with
(Mcinerny et al. unpubl. data). Secondly, local this type of data in mind (Solow 1993a, 1993b;
ity data allows use to determine both area of Burgman et al. 1995; McCarthy 1998; Solow &
occupancy (AOO) and extent of occurrence Roberts 2003; McInerny et al. unpubl. data). The
(EOO). In addition, where satellite images are methods differ in their usage. Some have been
available, the current existence of the former lo developed for use with limited data, some in
cation of a species may be ascertained, i.e., corporate the type of decline a species is likely
whether a former rain forest location has been to go through, and others include collection ef
cleared resulting in local extinction (Willis et al. fort or increase the comparability of results be
2003). This allows us to calculate the decline of tween different taxonomic groups of geograph
a species. Methods that use such data potentially ical regions.
have wide application as indicators of threat.
Using the Malagasy orchid, Angraecum ses
Using Locality Data to Measure Threat
qupidale, as an example, we show how herbar
and Extinction
ium data can be used to make IUCN Red List
Locality data allows use of GIS (Geographical
assessments.
Information Systems) to determine area of oc
cupancy (AOO), extent of occurrence (EOO),
METHODS AND MATERIALS
and number of subpopulations. Willis et al.
Statistical Models
(2003) used several methods to calculate these
Inferring Threat and Extinction Red List parameters.
Sightings of a species may be arranged as a Area of occupancy (AOO), according to the
SECOND IOCC PROCEEDINGS 301
FIGURE 2. Distribution of georeferenced herbarium specimens of Angraecum sesquepidale. Collections are
indicated as shaded circles, background is elevation with primary remaining vegetation highlighted (after Dupuy
& Moat 1996).
IUCN (2001), is the number of occupied cells; methods as for AOO or Rapoport's mean pro
however, no cell size is stated. Willis et al. pinquity (Rapoport 1982). Rapoport's mean pro
(2003) calculated the cell size as a tenth of the pinquity involves the construction of a mini
maximum distance between any pair of points. mum-spanning tree. From this, subpopulations
This allows the construction of a grid that is ap are separated, where the limb distance is more
propriate to the geographical range of a species. than twice the mean limb distance (Willis et al.
Extent of occurrence (EOO) is the shortest 2003).
continuous imaginary boundary enclosing a set
of points. Known as a convex hull, this is easily Application of Techniques
calculated within a GIS (Willis et al. 2003). Ac
cording to the IUCN (2001), "This measure may The statistical methods described here were
exclude discontinuities or disjunctions within the applied to the Malagasy orchid, Angraecum ses
overall distribution of taxa. " This measure, quepidale, using data from 32 herbarium collec
however, is difficult to implement, as boundaries tions that represent 21 localities (FIGURE 2) (J.
may be obscure (Willis et al. 2003). For exam Hermans unpubl. data).
ple, island distributions may be obvious, but
what do we do about mountain species?
RESULTS AND DISCUSSION
Calculation of number of subpopulations re
quires good knowledge of the species biology. Based on Solow (1993a), Solow & Roberts
Such knowledge, as mentioned previous, is rare (2003), and McInerny et al. (unpubl. data), p
ly available, since most species are only known values range from 0.60 to 0.77. These values are
from museum collections. Specimen locality high, particularly if compared with other species
data, however, may be used to calculate the of Malagasy orchids (Cribb et al., this issue).
number of contiguous cells, applying the same Application of GIS-based methods gave the fol-
302 SELBYANA Volume 26(1,2) 2005
FIGURE 3. Application of GIS-based techniques to the herbarium data of Angraecum sesquepidale.
lowing results (FIGURE 3): EOO = 225,493 krn2; unlikely. A further benefit is that these methods
AOO = 186,197 krn2 and three subpopulations are a way of standardizing assessments, thus
(Grid Adjacently); and Rapoport Analysis = five making species more comparable for prioritiza
sUbpopulations. The results suggest that Angrae tions.
cum sesquepidale should be classified under the The IUCN Red List criteria are themselves
IUCN Red List category as a species of Least not without criticism. Willis et al. (2003) pointed
Concern. out two examples. Firstly, the projected continu
ing decline criterion, according to the mCN
(2001), only requires a yes or no answer! Sec
CONCLUSIONS
ondly, regarding the fragmentation criterion, the
Natural history collections such as herbaria IUCN (2001) stated that habitat data can be used
offer a unique opportunity, using the methods in "certain circumstances," but no justification
described here, to rapidly assess the conserva was given or guidance offered on when habitat
tion status of much of the world's species, since data should be applied.
many are only known from these collections. Application of the statistical methods de
Such assessments will allow the prioritization of scribed here for inferring species decline from
our limited conservation funds and also will pre museum specimens can aid our understanding of
vent the undermining of potential conservation the probability of a taxon being threatened and
action for species on the brink of extinction. can help maintain public confidence in conser
Some may consider the results of these tech vation.
niques to be only preliminary assessments for
IUCN Red Listing; but, as pointed out here,
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