Recent Evolution and Divergence Among Populations of a Rare Mexican Endemic, Chihuahua Spruce, Following Holocene Climatic Warming

Ledig, F. Thomas; Jacob-Cervantes, Virginia; Hodgskiss, Paul D.; Eguiluz-Piedra, Teobaldo

doi:10.2307/2411004

Cited by 69 publications

(99 citation statements)

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“…Contrary to expectations based on their rarity (but see Comps et al 2001), studies on the genetic structure on Mexican and North American pinyon pines have shown high genetic variation (heterozygosities between 0.216 and 0.220) except for P. edulis (0.03, Premoli et al 1994) and a high population differentiation (F ST between 0.18 and 0.25). This genetic structure coincides with the one found in other rare conifer species like Picea chihuahuana (Ledig et al 1997) and suggests that the outcrossing rate is less than one as found for the few species where it has been estimated for P.maximartinezii, Ledig et al 2001. These data can now be studied under a phylogenetic approach.…”

Section: Introductionsupporting

confidence: 81%

Comparative genetic structure in pines: evolutionary and conservation consequences

Delgado

Cuenca

Escalante

et al. 2002

Rev. chil. hist. nat.

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Pines have been the focus of several studies that estimate population genetic parameters using both allozymes and chloroplast single sequence repeats (SSRs). Also, the genus has also been recently studied using molecular systematics so that we now have a more clear understanding of their evolutionary history. With this background we studied comparatively the genetic structure in pines. Expected heterozygosity is particularly constant with a 99 % confidence interval between 0.19 and 0.23 in species that have been studied until now using allozymes. There is a significant proportion of species (9/41) that show high population differentiation estimates (F ST = or larger than 0.15) and five of these have large and wingless seeds probably associated with low densities, bird dispersal mechanisms and resistance to water stress. These species include the North American pinyon pines. Outcrossing rates are also constant among species from both subgenus Pinus and subgenus Strobus, which probably reflects a selective limit to the amount of deleterious alleles that can be maintained in pine species and this also affects inbreeding levels. We also explored the data published using microsatellites in pines and conclude that these markers uncover a higher proportion of variation and genetic differentiation as expected and that the evolutionary models that are used to derive the population genetic structure estimators should take into account other sources of mutation (point mutations, larger insertions and or deletions and duplications) to better understand the comparative applications of these molecular markers.

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Section: Introductionsupporting

confidence: 81%

Comparative genetic structure in pines: evolutionary and conservation consequences

Delgado

Cuenca

Escalante

et al. 2002

Rev. chil. hist. nat.

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“…In contrast to the similar and high levels of polymorphisms observed at allozyme loci among the four spruce species studied here (Lagercrantz and Ryman, 1990;Ledig et al, 1997 andreferences therein, 2005), nucleotide variation was an order of magnitude lower in P. breweriana than in its boreal relatives. This low value is in agreement with the fossil record and with a mean Tajima's D value close to zero, both of which lent support to a scenario where P. breweriana retained a small population size since the Tertiary and through recent times.…”

Section: Polymorphism At Allozyme and Nucleotide Levelscontrasting

confidence: 42%

“…How will this be reflected in the estimates of current and ancestral effective population sizes? Second, expected levels of heterozygosity estimated from allozyme studies in different Picea species are surprisingly stable and fall between 0.1 and 0.3 in a majority of studies (Ledig et al, 1997). For example, in comparable surveys of genetic variation of allozymes in P. abies (Lagercrantz and Ryman, 1990) and P. breweriana (Ledig et al, 2005) values of the expected heterozygosity were 0.12 in both species, even though the population sizes of the two species today differ by several orders of magnitude.…”

Section: Introductionmentioning

confidence: 98%

New insights on the speciation history and nucleotide diversity of three boreal spruce species and a Tertiary relict

et al. 2009

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In all, 10 nuclear loci were re-sequenced in four spruce species. Three of the species are boreal species with very large natural ranges: Picea mariana and P. glauca are North American, and P. abies, is Eurasian. The fourth species, P. breweriana, is a Tertiary relict from Northern California, with a very small natural range. Although the boreal species population sizes have fluctuated through the Ice Ages, P. breweriana is believed to have had a rather stable population size through the Quaternary. Indeed, the average Tajima's D was close to zero in this species and negative in the three boreal ones. Reflecting differences in current population sizes, nucleotide diversity was an order of magnitude lower in P. breweriana than in the boreal species. This is in contrast to the similar and high levels of heterozygosity observed in previous studies at allozyme loci across species. As the species have very different histories and effective population sizes, selection at allozyme loci rather than demography appears to be a better explanation for this discrepancy. Parameters of Isolation-with-Migration (IM) models were also estimated for pairs of species. Shared polymorphisms were extensive and fixed polymorphisms few. Divergence times were much shorter than those previously reported. There was also evidence of historical gene flow between P. abies and P. glauca. The latter was more closely related to P. abies than to its sympatric relative P. mariana. This last result suggests that North American and Eurasian species might have been geographically much closer in the recent past than they are today.

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“…Therefore, in smaller isolated populations, the probability of mating occurring among relatives is higher than in larger populations that may present sufficient gene flow [5,56,57]. The amount of available pollen for fertilization in small and isolated populations may also cause ovule abortion and empty seeds in two different ways: First, insufficient pollen may increase selfing within individual trees, causing a greater proportion of empty seeds [58]; and second, some of the pollinated ovules will not be fertilized (presence of aborted first-year ovules) or will not develop normally (presence of aborted second-year ovules) [14,59,60]. Second-year aborted ovules were more numerous than first-year aborted ovules in both species, but the values of empty seeds and aborted ovules were higher in Rzedowski's pine than in veitchii pine.…”

Section: Contrasting Reproductive Indicatorsmentioning

confidence: 99%

“…When self-pollination occurs, the production of hormones stimulates ovule development, the seed is coated and the cones can be mature, but the seeds contained within are empty because of the effect of lethal alleles that prevent the normal development of embryos [15,60]. Embryonic degeneration is the result of the increased expression of lethal recessives in line with the increased homozygosity due to inbreeding [20,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]58]. Thus, with increased levels of selfing, higher numbers of empty seeds are found.…”

Section: Contrasting Reproductive Indicatorsmentioning

confidence: 99%

Reproductive Success and Inbreeding Differ in Fragmented Populations of Pinus rzedowskii and Pinus ayacahuite var. veitchii, Two Endemic Mexican Pines under Threat

Sánchez

Delgado-Valerio

Sáenz‐Romero

et al. 2016

Forests

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Abstract:Seed production, quality, germination and seedling establishment are indicators of reproductive success in conifers. Monitoring of these parameters is essential to determine the viability of populations for the purposes of conservation. We analyze cone and seed traits as indicators of reproductive success in the endangered Rzedowski´s pine (Pinus rzedowskii (Madrigal et Caballero) and near-threatened veitchii pine (Pinus ayacahuite var. veitchii (Shaw)) in west-central Michoacán, Mexico. These traits were systematically quantified and their variation assessed using Generalized Linear Mixed Models (GLMMs). We found that the reproductive success of Rzedowski's pine seems to be critical, presenting low seed efficiency (17.10%), germination (5.0%) and seedling establishment (27.7%), with high levels of inbreeding (0.79). In contrast, veitchii pine presents moderate seed efficiency (54.9%), high germination (71.5%) and seedling establishment (84%-97%) and low inbreeding (0.33). Reproductive indicators differed significantly among zones and populations for each species, where fragment sizes mainly affected seed production and efficiency. This result indicates that fragmentation has played a more important role in the reproductive success of Rzedowski's pine than in veitchii pine, perhaps by limiting pollen flow among zones and populations and producing higher levels of inbreeding and lower seed efficiency in the former species. We propose a conservation strategy for these important pine species in order to increase their long-term genetic viability.

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Recent Evolution and Divergence Among Populations of a Rare Mexican Endemic, Chihuahua Spruce, Following Holocene Climatic Warming

Cited by 69 publications

References 0 publications

Comparative genetic structure in pines: evolutionary and conservation consequences

Comparative genetic structure in pines: evolutionary and conservation consequences

New insights on the speciation history and nucleotide diversity of three boreal spruce species and a Tertiary relict

Reproductive Success and Inbreeding Differ in Fragmented Populations of Pinus rzedowskii and Pinus ayacahuite var. veitchii, Two Endemic Mexican Pines under Threat

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