Biological Flora of the British Isles: Gunnera tinctoria

Abstract

Summary1. This account presents information on all aspects of the biology of Gunnera tinctoria (Molina) Mirb. (G. chilensis Lam.; G. scabra Ruix & Pav.; G. pilosa Kunth) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. 2. Gunnera tinctoria is a gynomonoecious, clonal, perennial herb that is naturalized in parts of Britain, becoming invasive in parts of Ireland and, more recently, Scotland. It occurs where winter temperatures are mild, and precipitation and humidity are high. Gunnera tinctoria is native to South America, predominantly in the Andean region of Chile and Colombia, and probably in parts of Argentina, ranging from sea level to c. 2000 m a.s.l. 3. Typical habitats in Britain and Ireland include stream and river banks, lake and pond margins, coastal cliffs, as well as disturbed areas, such as roadsides, quarries and ditches. In its native range it occurs predominantly on the banks of rivers and streams, on coastal cliffs and within canopy gaps or at the margins of temperate-humid rain forests. 4. Gunnera tinctoria occurs on a variety of substrates, mainly on alluvial or colluvial soils derived from volcanic material or on thin gley soils of marine origin. In Ireland, it occurs naturally on soils with a pH ranging from 4.6 to 6.2 and has been cultivated in soils with a pH up to 7. Soil moisture content and soil organic matter vary greatly, although it rarely colonizes highly organic soils such as peat. It is susceptible to even mild water deficits at all stages of development, and its seedlings are also sensitive to waterlogged conditions. 5. Gunnera tinctoria produces large numbers of seeds and also spreads clonally, by a horizontal rhizome system. It is wind pollinated, although insect pollination has been reported in New Zealand. Seeds are likely to be predominantly water and/or bird dispersed. In its invasive range, it can form a large and persistent soil seed bank. Recruitment from seeds seems to be important for its initial establishment, while vegetative propagation is the main means of expansion, leading to dense clonal stands. Long-distance seed dispersal seems to be central to the colonization of new areas, although the transport of vegetative propagules may also be important. 6. Gunnera tinctoria is a strong competitor in its invasive range, particularly in wet, humid environments. Its competitive ability arises from its large stature, the persistence of its seeds and rhizomes and a capacity for fixing nitrogen through a unique intracellular symbiosis with cyanobacteria (Nostoc) that may be particularly important for supporting the rapid growth of established plants early in the spring.

Resource competition in plant invasions: emerging patterns and research needs

“…Invasive species may achieve dominance via an innately superior competitive ability over that of native species arising from physiological advantages that include high rates of resource acquisition (e.g., Eliason and Allen, 1997; Alpert et al, 2000; Callaway and Aschehoug, 2000; Rejmánek, 2000; Pyšek and Richardson, 2007; van Kleunen et al, 2010, 2011; Matzek, 2012; Funk, 2013), such as a capacity to fix nitrogen (e.g., Atwood et al, 2010; Le Maitre et al, 2011; Gioria and Osborne, 2013) or an ability to tolerate low resource availability (see Tilman, 1982; Weiner, 1993; Goldberg, 1996; Craine et al, 2005; Funk, 2013). Dominance can also be achieved via mechanisms that may interact with resource competition and that will be discussed throughout this paper, including: (1) competitive advantages arising from the release from natural enemies that are present in their native range but not in the invasive range (Enemy Release Hypothesis; ERH; Keane and Crawley, 2002; Mitchell and Power, 2003; Callaway et al, 2004; Maron et al, 2014); (2) an increased competitive ability post-introduction arising from evolutionary changes leading to a reallocation of resources from defense mechanisms that may be required in their native range, to growth and development (Evolution of Increased Competitive Ability; EICA; Blossey and Nötzold, 1995); (3) high phenotypic plasticity in traits that allow the survival and spread in areas characterized by novel conditions (Bossdorf et al, 2005; Richardson and Pyšek, 2006; Davidson et al, 2011); (4) trait differences between alien and native species arising from phylogenetic distinctiveness (Mack, 1996; Rejmánek, 1996) and potentially reflecting differences in the ecological niches that can be occupied.…”

“…Phenological differences resulting in early growth and in the initiation of significant size increases prior to those of native species may have a large impact on competitive interactions between invasive and native species (e.g., Tiley et al, 1996; Caffrey, 2001; Standish et al, 2001; Sala et al, 2007; Gioria and Osborne, 2010, 2013; Wilsey et al, 2011; Wolkovich and Cleland, 2011; Funk, 2013; Wolkovich et al, 2013). Early growth allows a species to exploit the available resources before other species and avoid competition for some resources during the initial stages of plant development.…”

“…However, jack-of-all-trade alien species can perform as well as natives under a broad range of environmental conditions, thus high resources or low environmental stresses are not good predictors of successful invasions. Many alien species have, in fact, invaded low-resource environments (Funk and Vitousek, 2007; Funk, 2013), including arid and semi-arid grasslands (Fowler, 1986), serpentines (e.g., Huenneke et al, 1990; O'Dell and Claassen, 2006; Vallano et al, 2012), or coastal dunes (e.g., French, 2012; Gioria and Osborne, 2013). Moreover, low nutrient availability may not affect competition (Kolb and Alpert, 2003) and, in one instance, low resources have been found to even promote invasions (Cleverly et al, 1997; see Funk, 2013).…”

Journal of Ecology News

“…Last but not least, four new accounts were published in the Journal's long-standing series Biological Flora of the British Isles: Gunnera tinctoria (Gioria & Osborne 2013), Pulmonaria officinalis (Meeus et al 2013), Robinia pseudoacacia (Cierjacks et al 2013) and Silene suecica (Nagy 2013). Readers interested in preparing a Biological Flora account should contact the Biological Flora Editor Tony Davy.…”

“…Zamin & Grogan's (2013) article on caribou browsing in low Arctic tundra created much interest because of the implications for climate change. The Irish Times carried an article "Gunning for Gunnera" following publication of Gioria & Osborne's (2013) Biological Flora account of Gunnera tinctoria. Catering to the public's interest in R-rated themes, the Los Angeles Times carried an article "Mosses lose their sex drive on islands" summarizing Patiño et al's (2013) paper "Baker's law and the island syndromes in bryophytes".…”