Threats from Alien Plant Species in the Galápagos Islands

Mauchamp, André

doi:10.1046/j.1523-1739.1997.95356.x

Cited by 95 publications

(71 citation statements)

References 8 publications

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“…Their analysis of pollen and plant macrofossils suggests that all six pollen taxa were present thousands of years before the onset of human impact. Establishing this evidence for the native status of these plants is relevant to the issue of non-native species management and ecosystem restoration in the Galápagos Archipelago (Mauchamp 1997).…”

Section: Palynologymentioning

confidence: 91%

A Paleoecological Perspective on Wetland Restoration

Williams

2011

Wetlands

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Paleoecological investigations of wetland sedimentary deposits offer the possibility of obtaining accurate reconstructions of base line conditions in the past. Plant remains, such as leaves, seeds, fruits, wood, and pollen, provide a window of variable temporal and spatial resolution into past environmental conditions at a particular site. These archives of physical and biological wetland ecosystem characteristics, if preserved, may be exploited to reconstruct the plant community at a single point in time. Moreover, changes in past plant community composition, hydrology, and the dynamics of wetland ecosystems through time may be better understood. This paper reviews the range of paleoecological information archived in wetland sedimentary deposits that may be understood in the restoration science context. This type of information gleaned by applying paleoecological techniques should provide reasonable targets for restoration ecologists working to improve the quality and quantity of ecosystem functions and services in wetlands.Undisturbed wetlands, by virtue of their position on the landscape and the specific properties of the plants that populate these ecosystems, archive proxies of past environmental information within their soils and sediments. In temperate North America the geomorphic settings for wetlands typically vary from locale to locale, including depressional, riverine or floodplain, and lacustrine, among others. Yet all wetlands share a common attribute; the inundation of soil by water at a duration or frequency that is sufficient to exclude flora and fauna intolerant of such conditions. Although this ecosystem trait provides wetland scientists a means to mechanistically define a wetland, from a paleoecological standpoint there is a more important consequence of hydric soil conditions; plant and animal remains are often preserved in the wet, oxygen-deficient soils. Moreover, most wetlands are depositional environments; places where sediment accumulation exceeds erosion, thereby providing B. A. LePage (ed.), Wetlands,

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Section: Palynologymentioning

confidence: 91%

A Paleoecological Perspective on Wetland Restoration

Williams

2011

Wetlands

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“…With noticeable human impacts even in Darwin's time, Floreana Island now has the longest history of human settlement and avian extinctions in the entire Galápagos archipelago. Native habitat on Floreana Island has been disturbed via agricultural clearance (Lack 1947, Sulloway 1982, Steadman 1986, and invaded by introduced plants (Mauchamp 1997, BirdLife International 2009a, predators (Curry 1986, Baskin 2002, Grant et al 2005, and avian parasites and infectious diseases (Fessl and Tebbich 2002. To date, three Darwin's finch species have become extinct on Floreana Island, including both the Large Ground Finch Geospiza magnirostris and Sharp-beaked Finch G. nebulosa by about 1870 (reviewed in Sulloway 1982, Steadman 1986) and the reported loss of the Warbler Finch Certhidia fusca by 2004 (see Grant et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

O’Connor

Sulloway

Kleindorfer

2010

Bird Conservation International

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SummaryIsland species typically exist in pathogen and predator sparse environments before human settlement, and are particularly vulnerable to the impacts of invasive species. In this study, we used the variable circular-plot method to estimate the density of birds in the highlands of Floreana Island, Galápagos Archipelago, where introduced parasites, predators, and habitat degradation are a known threat to endemic species. We recorded the number of birds seen and heard at 15 locations near Cerro Pajas Volcano in 2004 and 2008, an area that harbours the largest expanse of highland Scalesia forest on Floreana Island. We estimated the change in population density for nine bird species, including five species of Darwin’s finches. We specifically address changes in population density for the locally endemic Medium Tree Finch Camarhynchus pauper, which only occurs on Floreana Island and has a small population size. Comparing 2004 and 2008, our study found lower population density in the Medium Tree Finch, but stable population density in Small Tree Finch C. parvulus and Large Tree Finch C. psittacula. Based on data from three additional highland sites surveyed in 2008, we estimate that the maximum size of the Medium Tree Finch population is 1,620 individuals. In addition to the survey data, we observed breeding males in 2006 and 2008. We found: (1) low nesting success (six out of 63 nests produced fledglings) and high Philornis downsi parasite intensity, and (2) a biased age structure of the breeding population. No breeding males were one year old in 2006, and no males were five years old in either study year, indicating low reproductive success as well as limited lifespan. This research has contributed to the recent re-evaluation by IUCN, which has changed the Red List status of the Medium Tree Finch from ‘Vulnerable’ to ‘Critically Endangered’.

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“…Linear increases have been shown in the number of introduced plants known in New Zealand (Owen 1998) and the number of introduced insects in Hawaii (Beardsley 1991). In Galapagos, the rise in the reported number of introduced vascular plant species appeared to be exponential (Mauchamp 1997), and Peck et al (1998) reported an exponential increase in introduced insects. What is termed here 'introduction rate' takes no account of species that were introduced but died out before they could be registered by science.…”

Section: Introductionmentioning

confidence: 99%

“…Relationships between human population and alien species numbers (e.g. Mauchamp 1997;Chown et al 1998;McKinney 2001) might help to explain the link between human population density and threats to native biodiversity (McKee et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Can We Infer Island Introduction and Naturalization Rates from Inventory Data? Evidence from Introduced Plants in Galapagos

Tye

2006

Biol Invasions

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Studies of human-mediated rates of introduction of organisms to islands are few, results fall into two models (linear and exponential), and relationships with human population and activities are obscure. Owing to their late settlement and good scientific record, data from Galapagos may be exceptionally informative. The rate of introduction of vascular plant species to Galapagos has been suggested to be exponential, paralleling the rise in human population. However, detailed reconstruction of growth in numbers of introduced plant species, based on historical and recent records, reveals changes in study criteria over the last two centuries, which obscure the true introduction rate. At first, cultivated species were deliberately excluded from most studies. From the 1960s, naturalized cultivated species were included more consistently, but non-naturalized species were still excluded. From the mid-1980s, the latter were deliberately included. Accidental introductions increased linearly from 1807 (the first records) to the present. Escapes from cultivation show increases in rate around 1906 and in the period 1970-1990, the latter coinciding with the first studies directed at areas affected by human activities. Non-naturalized cultivated species rose abruptly from the late 1980s, as they became deliberately studied. There seems to be no direct link with human population size. Data represent rate of discovery rather than true introduction rate, and the changing overall rate reflects changing botanical interests and research effort. Data from other islands also suggest that linear increases in naturalized plants are the norm. Galapagos data do not permit confident statements about the introduction rate of cultivated species, but suggest that this may depend more on human activities than human population size. ResumenLos estudios de la tasa de introduccio´n de los organismos a islas causada por los seres humanos son pocos; sus resultados caben dentro de dos modelos (linear y exponencial), y la relacio´n con la poblacio´n humana y sus actividades es oscura. Los datos de Gala´pagos pueden ser excepcionalmente informativos, debido a su colonizacio´n tardı´a y registro cientı´fico bueno. Se ha sugerido que la tasa de introduccio´n de las plantas vasculares a Gala´pagos es exponencial, en paralelo al crecimiento de su poblacio´n humana. Sin embargo, una reconstruccio´n detallada del incremento en nu´mero de especies de plantas introducidas, basada en los datos histo´ricos y recientes, revela cambios en los criterios de estudio durante los u´ltimos dos siglos, lo que oscurece la verdadera tasa de introduccio´n. Al principio, se excluı´an de la mayorı´a de los estudios las especies cultivadas. Desde los 1960, se incluyeron con ma´s regularidad las especies cultivadas naturalizadas, mientras las no-naturalizadas quedaban excluidas. Desde los 1980, estas u´ltimas fueron intencionadamente incluidas. Las especies de introduccio´n accidental demuestran un aumento linear en su nu´mero desde 1807 (los primeros registros) hasta la presen...

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Threats from Alien Plant Species in the Galápagos Islands

Cited by 95 publications

References 8 publications

A Paleoecological Perspective on Wetland Restoration

A Paleoecological Perspective on Wetland Restoration

Avian population survey in the Floreana highlands: is Darwin’s Medium Tree Finch declining in remnant patches ofScalesiaforest?

Can We Infer Island Introduction and Naturalization Rates from Inventory Data? Evidence from Introduced Plants in Galapagos

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