Responses of ferns and lycophytes to global climate change are difficult to predict and have been little studied. Because spores provide ferns and lyco-phytes with superior long-distance dispersal capabilities, these groups may have an advantage over seed-bearing plants in adapting to climate changes (Given, 1993). However, increased habitat fragmentation, physiological stress, and habitat disturbance may cause local or global extinctions of fern and lycophyte species that are unable to survive the changing environmental conditions (Given, 1993). Kelsall et al. (2004) compared population census data to climate data for
Phyllitis scolopendrium var. americana, limited to 17 known colonies in New York. They found climate was not responsible for much fluctuation in population size, but the authors concluded that this fern species is limited in distribution by the limited occurrence of habitat that can buffer it from climatic fluctuations (Kelsall et al., 2004). With the thinning of the ozone layer, vegetation is exposed to increased ultraviolet-B solar radiation, but there has been little experimental research on the effects of this increased exposure within ferns and lycophytes (Bjorn, 2007). The aquatic fern Azolla microphylla exhibited reduced growth and reduction in its cyanobacterial nitrogen fixation when exposed to ultraviolet-B radiation (Jayakumar et al., 2002), and also curling of the fronds and chlorosis (Jayakumar et al., 1999). However, the lycophyte Lycopodium annotinum did not show growth inhibition when exposed to ultraviolet-B radiation that replicated conditions of 15% ozone thinning (Bjorn, unpublished results). Additional research on fern and lycophyte responses to climate change is much needed.
It is important to keep in mind the various life cycle stages of ferns and lycophytes when discussing their protection, conservation, and restoration. Research on spore production, dispersal, viability, and soil spore banks has demonstrated important differences compared with similar research on seed plants. As each fertile frond often produces millions of spores (Peck et al., 1990; see Chapter 9), spores can often be found aerially suspended at high altitudes. For instance, a fern sporangium was trapped by airplane as high as 2400 meters above the Hawai'ian Islands (Gressitt et al., 1961). The closed forest is less easily penetrated by wind, however, and often spores are dropped within the vicinity of the parent plant (Conant, 1978).
Research and knowledge concerning the storage banking of spores has recently advanced, and identifying ideal conditions of storage to maximize spore viability is an important component of ex situ fern and lycophyte conservation (see Chapter 11). Studies have identified variation by taxon for ideal spore storage conditions with temperature, moisture, and storage duration (Aragon and Pangua, 2004; Cha-Cha et al., 2005). Additional studies have determined the effects of cryopreservation techniques on spore viability (Pence, 2002) and game-tophyte/sporophyte development (Ballesteros et al., 2006) with promising results.
Protecting soil spore bank resources and promoting in situ germination has been suggested for the conservation of rare fern taxa (Dyer and Lindsay, 1996), and there is evidence for persistent soil spore banks (Sheffield, 1996; LaDeau and Ellison, 1999; Ranal, 2003; Ramirez-Trejo et al., 2004). However, the longevity of spores in the soil spore bank varies by taxon and habitat (Ranal, 2003). The viability of tree bark spore banks has also been studied, and interestingly was not observed to be affected by dry seasonality (Ranal, 2004).
The gametophytic stage of ferns and lycophytes is particularly challenging to conservation biologists because of the small size and obscurity of gametophytes (see Chapter 9). Knowledge is growing of gametophyte development and survival in situ (see Sheffield, 1996; Bernabe et al., 1999; Ranal, 2004), but further research on in situ gametophyte ecology and sporeling establishment is still urgently needed (Dyer and Lindsay, 1996; see Chapters 2 and 9). Many laboratory studies have been conducted on spore germination and gametophyte development, and mechanisms have been identified which prevent self-fertilization (see Chapters 5 and 9), and promote continuous recruitment of gametophytes by intermittent spore germination (Gomes et al., 2006).
Fern and lycophyte sporophytes have been the most prevalently studied, with a focus on sporophyte development and growth rate, species distribution and diversity, and phylogenetic relationships. Ecological studies of ferns and lyco-phytes and the roles they play in plant communities have been historically rare, but are increasingly needed to inform restoration efforts and plan conservation reserves (see Chapter 8).
Propagation research for rare or threatened ferns and lycophytes is essential, and ex situ collections of sporophytes and spores provide a genetic safety net helping to prevent species extinction. Ex situ horticultural propagation of endangered fern and lycophyte species may also reduce harvesting pressures on wild populations if they are made commercially available (Gibby and Dyer, 2002). Propagation techniques specific to certain threatened or endangered taxa have been developed that ensure the most efficient and successful results, including propagation from rhizome cuttings and stipules (Wardlaw, 2002a, 2002b; Zenkteler, 2002; Chiou et al., 2006). For instance, the endangered epiphytic fern Drynaria quercifolia was propagated from spore to gametophyte to sporophyte within 4 months, and whole plants were produced from field-grown rhizome explants within 3 months (Hegde and D'Souza, 1996). See Chapter 11 for a thorough review and discussion of ex situ conservation of ferns and lycophytes.
Tropical ferns and lycophytes are especially threatened in areas of high endemism throughout the world (Gomez-P., 1985). To preserve the maximum biodiversity, conservationists must concentrate efforts on biodiversity hotspots and areas of high endemism. Generally, sites of high productivity support higher species diversity (Lehmann et al., 2002), and oceanic islands are also acknowledged as important endemism centers (Given, 1993). For example, 70% of the Hawaiian Island fern and lycophyte flora is endemic (Gagne, 1988). Evidence suggests that the fern flora of east Malesia dispersed from New Guinea and in isolation evolved into several new species (Kato, 1993).
Predictive factors for areas of higher fern and lycophyte endemism and biodiversity generally include terrain and climate (Pausas and Saez, 2000), and more particularly, regional mean annual temperature and water availability (Lehmann et al., 2002), soil fertility and distance from nearest geological refugium (Lwanga et al., 1998), soil composition and elevation (Duncan et al., 2001; Banaticla and Buot, 2005), and water availability and landscape heterogeneity (Bickford and Laffan, 2006). A pattern emerges between the distribution of endemism and elevation in tropical mountainous areas, where the highest endemism has been observed at mid-elevations in Costa Rica (Watkins et al., 2006), though endemic species at highest elevations are often more common than widespread species (Kluge and Kessler, 2006). Similarly in Peru, fern and lycophyte diversity and endemism are found to concentrate at higher elevation, especially in humid montane forests (Leon and Young, 1996b).
Smith (2005) has produced a thorough summary of the published regional fern and lycophyte floras and annotated checklists, or lack thereof, which is generally summarized here. Most tropical and subtropical countries/regions are lacking in complete modern fern and lycophyte floras, except Mexico, Mesoamer-ica, parts of the Antilles, New Zealand, Hawaii, and the Mariana Islands (Smith, 2005). Meanwhile, treatments of fern and lycophyte flora are in progress for Bolivia, East Africa, Venezuela, and China (Smith, 2005). Areas with annotated checklists only include tropical East Africa, Malaysia, and Mount Kinabalu, and areas of partially written floras include Ecuador and Malesia (Smith, 2005). A project to produce an annotated checklist of Sulawesi ferns and lycophytes of Indonesia was also reported underway to encourage further interest in study of the poorly documented fern flora there (Camus and Pryor, 1996). Hotspots with inadequate or outdated floras include Colombia, Brazil, Madagascar, New Guinea, and the Himalayas (Smith, 2005). These regions are noted as important areas of fern and lycophyte diversity, and it is likely that the regional gaps are large and numerous for modern, complete fern and lycophyte floras. Assessments of fern and lycophyte diversity and rarity have also been published for the Askot Wildlife Sanctuary in West Himalaya, India (Samant et al., 1998), the Orongorongo Valley Field Station in New Zealand (Fitzgerald and Gibb, 2001), the Pitcairn Islands (Kingston and Waldren, 2002), and the Prespa National Park of Greece (Pavlides, 1997), among others. These reports, though not conclusive for generalization across entire countries or regions, nonetheless provide valuable insights as to locating potential areas and taxa of high conservation priority.
Previous studies of threatened and rare ferns and lycophytes in various regions are not encouraging, as many species fall within these categories and several are reported to be near extinction. For instance, ferns and lycophytes from Trinidad and Tobago were assigned a risk index rating, and approximately half of the ferns there are deemed possibly at risk (Baksh-Comeau, 1996). Federal protection within the USA (i.e., those species listed by the US Fish and Wildlife Service as threatened or endangered) includes only one third of ferns and fern allies that are currently at risk (Stein et al., 2000). Of the 22 rare species of ferns and lycophytes assessed from the islands of Sao Tome e Principe (Gulf of Guinea), IUCN Red List Categories were assigned as eight species critically endangered, three endangered, and eleven vulnerable (Figueiredo and Gascoigne, 2001). Fifty percent of the ferns and lycophytes of the Pitcairn Islands have also been assigned to an IUCN threat category, with invasive species, habitat degradation, reduced population and distribution, and over-harvesting listed as the most prevalent threats (Kingston and Waldren, 2002). Similarly, rare ferns in Russia are threatened due to their dependence on restricted habitats, which are additionally stressed by human impacts (Guryeva, 2002). Fern conservation in south tropical Africa faces other obstacles to conservation initiatives that include disrupted economies, civil war, and increased human population pressure on crucial fern habitat (Burrows and Golding, 2002). And in Brazil, habitat degradation, commercial extraction, and lack of population data are considered the largest threats to fern and lycophyte species (Windisch, 2002).
However, an encouraging side-effect of human impact might be found in that the dispersal of ferns in Germany seems to be facilitated by transportation corridors. A study found ferns at more than 90% of railway stations examined, including species on the Red List for Germany (Wittig, 2002). Another encouraging side-effect of human impact was measured by Jamir and Pandey (2003); they found high species richness, high endemism, and high presence of other rare and primitive species of ferns and lycophytes in sacred forest groves of the Jainita Hills in northeast India. Tribal communities have designated these protected areas as part of their religious tradition, and the natural biodiversity preserved there "since time immemorial" (Jamir and Pandey, 2003, p. 1497).
Forest destruction and shifting cultivation are considered the most serious threat to fern and lycophyte habitat and diversity in the Philippines (Amoroso et al., 1996). A diversity assessment found 275 species of ferns and lycophytes at Mount Kitanglad, 249 species at Mount Apulang, and 183 species at Marilog Forest (Amoroso et al., 1996). Of these, a status determination revealed one endangered species, 45 rare, seven depleted, 89 endemic, and 81 economically important (Amoroso et al., 1996). An updated account of Philippines fern and lycophyte diversity calls for more botanical explorations in the Philippines and other tropical regions, as results of field explorations included the rediscovery of the genus Cyrtomium, and the rediscovery of rare endemics Aglaomor-pha cornucopia, Antrophyum williamsii, Ctenitis humilis, and Dennstaedtia macgregori (Barcelona, 2005). The fern and lycophyte floras of tropical regions must be further surveyed, described, and assessed for conservation priority.
The IUCN Red List 2004 categorized approximately 67% of the evaluated species of ferns and allies as threatened (140 out of 210 evaluated species) (Baillie et al., 2004; see www.redlist.org). Although the species evaluated by IUCN only represent 1.6% of the total described species (13 025), they are representative of a large geographical distribution across the world (Baillie et al., 2004). Nevertheless, ferns and lycophytes as a highly diverse group are substantially underrepresented on the IUCN Red List, and it is critical that many more species be evaluated in the near future (Baillie et al., 2004).
Isoetes has been noted as rare and threatened across several regions and countries. Only two natural populations of Isoetes sinensis are known to exist and both are threatened in mainland China, where populations have decreased by 50% within the last 4 years, most probably due to destruction of wetland habitat (Wang et al., 2005). Isoetes georgiana is now known from 12 locations on the Georgia coastal plain rather than being limited to one location as previously reported; yet this species is still considered rare (Brunton and Britton, 1996). The Andean highlands of Peru were found to contain eight species of Isoetes, of which four are endemic, and these highland areas have been impacted by mining pollution and drainage, agriculture, and grazing (León and Young, 1996a). Musselman (2002) reports that the single species of Isoetes in Syria (I. olympica) is reduced to 100 individuals and threatened with extinction by regional irrigated agriculture. All four species of Isoetes in China, (I. hypsophila, I. sinensis, I. yunguien-sis, and I. taiwanensis) are critically endangered and at risk of extinction due to habitat loss and degradation, water pollution, and competitive exclusion by invasive species (Liu et al., 2005). Within the continental USA, Isoetes, Botrychium, and Selaginella are the top three genera with the highest number of threatened ferns and lycophytes (Grund and Parks, 2002).
Additional ferns that are sparsely distributed and depend upon restricted habitat, such as the newly described New Zealand fern Asplenium cimmeriorum of cave entrances, are of high conservation priority due to their vulnerability to over-collection and disturbance (Brownsey and deLange, 1997). Hymenophyllum tunbrigense, discovered within the last 10 years in a small area in the western part of the Vosges Mountains, occurs only in Abies alba forests on moist sandstone rocks less than 2.5 m high, and requires dense forest canopy for continuous shade and protection from storms (Muller et al., 2006). Mankyua chejuense is recommended to be listed as critically endangered, as it is limited to five extant subpopulations and 1300 individuals in the Republic of Korea, and depends on basaltic rock microhabitat (Kim, 2004). And in the Hawaiian Islands, all six species of the endemic fern Diellia are considered of conservation priority due to their restricted distribution (five species are single-island endemics) and small population sizes (Aguraiuja et al., 2004). Ferns and lycophytes with restricted distribution and reduced population sizes are of highest risk of extinction, especially within degraded or vulnerable landscapes.
10.8 Genetics in fern and lycophyte conservation strategies
Phylogenetic relationships among ferns and lycophytes and evolutionary biogeographical theory are advancing with the use of molecular system-atics and population genetics (see Chapter 4). These phylogenetic studies are important in helping us to understand evolutionary relationships and dispersal patterns among fern and lycophyte taxa (see Chapters 12-16). To explain the evolutionary biogeography of fern floras, research needs to include species-specific biogeographies and analyses of historical large-scale environmental change such as climatic and geological events, which can then be tested and substantiated (or disproved) with molecular methods (e.g., Kato, 1993). Differentiating between dispersal and vicariance in historical patterns of fern biogeography is difficult and needs further study (Wolf et al., 2001).
The erosion of genetic diversity - whether through reduced abundance, loss of unique populations, or extinction of entire species - is the main evil that fern and lycophyte conservation geneticists strive to prevent. Analyses of species-specific genetic diversity aim to identify levels and patterns of genetic variability across time and space (Ranker et al., 1996; Rumsey et al., 1999; Machon et al., 2001), to assess population-level genetic diversity to inform conservation goals and management priorities (Ranker, 1994; Eastwood et al., 2002; Kingston et al., 2004; Su et al., 2004, 2005; Wang et al, 2004; Chen et al., 2005; Kang et al., 2005), and to determine whether morphologically variant populations should be classified as subspecies or distinct species (Perrie et al., 2003). To prevent inbreeding depression in fragmented landscapes and reduced populations, it is suggested to treat each as separate parameters in analyses to identify genotype-specific phenomena from population parameters (Ouborg et al., 2006). The key to these approaches is their integration of genetic and ecological data for a more accurate understanding of conservation needs in the present.
10.9 Protection and restoration
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