INVESTIGADORES
MATHIASEN Paula
congresos y reuniones científicas
Título:
Genetic effects of forest fragmentation in Patagonia: species sensitivity is dependant on life history traits
Autor/es:
PREMOLI, ANDREA C.; MATHIASEN, PAULA; SOUTO, CINTIA P.; ROVERE, ADRIANA E.; VERGARA, RODRIGO; LARA, ANTONIO; NEWTON, ADRIAN C.
Lugar:
S.C. de Bariloche, Rio Negro, Argentina
Reunión:
Workshop; Workshop on forest fragmentation in South America: understanding biodiversity loss; 2006
Resumen:
Conservation genetics seeks to understand anthropogenic detrimental effects on biodiversity loss at the gene/genotypic level. Conversion of continuous habitats into smaller patches reduces population size and increases population isolation. Thus, populations lose genetic variation because of genetic drift and suffer from elevated inbreeding and restricted gene flow. These processes lead to fixation of deleterious alleles and inbreeding depression, reducing survival and fecundity and therefore impacting on the long term viability of populations. We present two case studies to show long-lasting and recent effects of forest fragmentation in Patagonia. We test the hypothesis that species-sensitivity to fragmentation depends on species-specific life history traits, with the corresponding genetic consequences on isozyme polymorphism. Forest fragmentation occurred in Patagonia since the early Spanish colonization when most valuable logging species as Fitzroya cupressoides were decimated from accessible sites. We analyzed levels of genetic variation and divergence of remnant stands within the Central Depression of southern Chile. Genetic polymorphisms of 21 populations were geographically structured. Lowland populations have high within-population isozyme variation and they clearly differentiate from those on the coast or the Andes (Premoli et al. 2003). Results suggest long-term persistence due to historical factors. Full-glacial conditions probably resulted in altitudinal lowering of the cold-resistant elements such F. cupressoides which survived locally (Markgraf et al. 1995; Villagrán et al. 2006). Recent fragmentation in southern Chile was studied on Embothrium coccineum, an early colonizer, and bird-pollinated tree. We analyzed genetic parameters of adults and greenhouse-grown progeny of spatially isolated trees and different sized fragments. We measured vigor parameters and outcrossing rates on progeny arrays. Genetic traits of adults did not correlate significantly with population size, as expected, given that fragmentation is relatively recent. Seeds from small fragments had the highest germination success and outcrossing rates, suggesting that higher pollinator activity in such fragments reduces selfing, buffering genetic erosion and maintaining adaptive variation (Mathiasen 2004). A limited effect of fragmentation, i.e. low-sensitivity, on genetic structure of E. coccineum was detected in small fragments probably due to its self-incompatible reproductive system so enforced outbreeding counteracts genetic erosion and inbreeding. In contrast, remnant stands of the slow-growing F. cupressoides from the Central Depression, which in turn represent an extreme case of deforestation due to habitat loss (Fraver et al. 1999), are isolated from continuous stands. Hence, they have high-sensitivity to fragmentation and are in urgent need of conservation actions to preserve gene flow rates with other more distant populations. Fitzroya cupressoides were decimated from accessible sites. We analyzed levels of genetic variation and divergence of remnant stands within the Central Depression of southern Chile. Genetic polymorphisms of 21 populations were geographically structured. Lowland populations have high within-population isozyme variation and they clearly differentiate from those on the coast or the Andes (Premoli et al. 2003). Results suggest long-term persistence due to historical factors. Full-glacial conditions probably resulted in altitudinal lowering of the cold-resistant elements such F. cupressoides which survived locally (Markgraf et al. 1995; Villagrán et al. 2006). Recent fragmentation in southern Chile was studied on Embothrium coccineum, an early colonizer, and bird-pollinated tree. We analyzed genetic parameters of adults and greenhouse-grown progeny of spatially isolated trees and different sized fragments. We measured vigor parameters and outcrossing rates on progeny arrays. Genetic traits of adults did not correlate significantly with population size, as expected, given that fragmentation is relatively recent. Seeds from small fragments had the highest germination success and outcrossing rates, suggesting that higher pollinator activity in such fragments reduces selfing, buffering genetic erosion and maintaining adaptive variation (Mathiasen 2004). A limited effect of fragmentation, i.e. low-sensitivity, on genetic structure of E. coccineum was detected in small fragments probably due to its self-incompatible reproductive system so enforced outbreeding counteracts genetic erosion and inbreeding. In contrast, remnant stands of the slow-growing F. cupressoides from the Central Depression, which in turn represent an extreme case of deforestation due to habitat loss (Fraver et al. 1999), are isolated from continuous stands. Hence, they have high-sensitivity to fragmentation and are in urgent need of conservation actions to preserve gene flow rates with other more distant populations. Embothrium coccineum, an early colonizer, and bird-pollinated tree. We analyzed genetic parameters of adults and greenhouse-grown progeny of spatially isolated trees and different sized fragments. We measured vigor parameters and outcrossing rates on progeny arrays. Genetic traits of adults did not correlate significantly with population size, as expected, given that fragmentation is relatively recent. Seeds from small fragments had the highest germination success and outcrossing rates, suggesting that higher pollinator activity in such fragments reduces selfing, buffering genetic erosion and maintaining adaptive variation (Mathiasen 2004). A limited effect of fragmentation, i.e. low-sensitivity, on genetic structure of E. coccineum was detected in small fragments probably due to its self-incompatible reproductive system so enforced outbreeding counteracts genetic erosion and inbreeding. In contrast, remnant stands of the slow-growing F. cupressoides from the Central Depression, which in turn represent an extreme case of deforestation due to habitat loss (Fraver et al. 1999), are isolated from continuous stands. Hence, they have high-sensitivity to fragmentation and are in urgent need of conservation actions to preserve gene flow rates with other more distant populations. E. coccineum was detected in small fragments probably due to its self-incompatible reproductive system so enforced outbreeding counteracts genetic erosion and inbreeding. In contrast, remnant stands of the slow-growing F. cupressoides from the Central Depression, which in turn represent an extreme case of deforestation due to habitat loss (Fraver et al. 1999), are isolated from continuous stands. Hence, they have high-sensitivity to fragmentation and are in urgent need of conservation actions to preserve gene flow rates with other more distant populations.