Population-size effects on seeds and seedlings from fragmented eucalypt populations: implications for seed sourcing for ecological restoration

2007 ◽  
Vol 55 (3) ◽  
pp. 390 ◽  
Author(s):  
Siegfried L. Krauss ◽  
Luise Hermanutz ◽  
Stephen D. Hopper ◽  
David J. Coates
Keyword(s):  
Population Size ◽  
Ecological Restoration ◽  
Seed Production ◽  
Size Effects ◽  
Seedling Survival ◽  
Seed Maturation ◽  
Source Population ◽  
Long Distance ◽  
Fragmented Populations ◽  
Fitness Effects

Ecological restoration of degraded habitats is a major conservation activity requiring the collection of large amounts of native seed. Seed production and the genetic quality of seed may be influenced by properties of the source population, such as population size and fragmentation, potentially having an impact on restoration goals. We assessed the population-size effects on seed production and seedling performance in two Western Australian wheatbelt eucalypts, Eucalyptus salmonophloia F.Muell. and E. salubris F.Muell. Both species were historically widespread and dominant, but, as a consequence of land-clearing for agriculture, now exist as small, highly fragmented populations throughout the western half of their range. Given their former importance in the landscape, these species will be critical in ecological restoration of the region. We assessed small (n = 6–12) and large (n > 200) remnant populations in a highly fragmented landscape and compared these to large unfragmented populations. Seed number per capsule was dependent on population size and fragmentation for E. salubris, but not for E. salmonophloia. Large, unfragmented populations of E. salubris produced more than twice the number of seeds per capsule (mean = 2.95) than small and/or fragmented populations. However, seed germination, seed weight, seedling survival and seedling vigour to 1 year were independent of population size or fragmentation in both species. Our results suggest that reduced population size and increased fragmentation can negatively affect pollen quantity and/or quality, thereby limiting seed production, although no fitness effects were observed post-seed maturation. We suggest that the relative absence of post-seed maturation fitness effects in these small fragmented populations are a consequence of (1) wide outcrossing resulting from long-distance dispersal of pollen by highly mobile birds among fragmented populations and/or (2) efficient pre- or post-zygotic selection against more homozygous zygotes within fruits so that only relatively outbred seeds mature. The consequences on seed collection for ecological restoration of reduced population size and increased fragmentation for these eucalypts may be fewer seeds for the same collecting effort, but no apparent fitness effects of mature seeds. However, caution should be exercised when harvesting seed from these smaller populations, as over-harvesting may have an impact on recruitment and hence long-term persistence.

scholarly journals The distribution of mutational effects on fitness in Caenorhabditis elegans inferred from standing genetic variation

2020 ◽  
Author(s):  
Kimberly J. Gilbert ◽  
Stefan Zdraljevic ◽  
Daniel E. Cook ◽  
Asher D. Cutter ◽  
Erik C. Andersen ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Caenorhabditis Elegans ◽  
Population Size ◽  
Genomic Structure ◽  
Random Mating ◽  
Population Substructure ◽  
C Elegans ◽  
Fitness Effects ◽  
Self Fertilization ◽  
New Mutations

ABSTRACTThe distribution of fitness effects for new mutations is one of the most theoretically important but difficult to estimate properties in population genetics. A crucial challenge to inferring the distribution of fitness effects (DFE) from natural genetic variation is the sensitivity of the site frequency spectrum to factors like population size change, population substructure, and non-random mating. Although inference methods aim to control for population size changes, the influence of non-random mating remains incompletely understood, despite being a common feature of many species. We report the distribution of fitness effects estimated from 326 genomes of Caenorhabditis elegans, a nematode roundworm with a high rate of self-fertilization. We evaluate the robustness of DFE inferences using simulated data that mimics the genomic structure and reproductive life history of C. elegans. Our observations demonstrate how the combined influence of self-fertilization, genome structure, and natural selection can conspire to compromise estimates of the DFE from extant polymorphisms. These factors together tend to bias inferences towards weakly deleterious mutations, making it challenging to have full confidence in the inferred DFE of new mutations as deduced from standing genetic variation in species like C. elegans. Improved methods for inferring the distribution of fitness effects are needed to appropriately handle strong linked selection and selfing. These results highlight the importance of understanding the combined effects of processes that can bias our interpretations of evolution in natural populations.

scholarly journals El ambiente de la semilla en el suelo: su efecto en la germinación y en la sobreviviencia de la plántula

2017 ◽  
pp. 73
Author(s):  
Lourdes González-Zertuche ◽  
Alma Orozco-Segovia ◽  
Carlos Vázquez Yanes
Keyword(s):  
Ecological Restoration ◽  
Native Plants ◽  
Seedling Survival ◽  
Physiological Responses ◽  
Seed Banks ◽  
Seed Vigor ◽  
Ecological Significance ◽  
Ecological Traits ◽  
Soil Burial ◽  
Adverse Conditions

<p>Conservation and ecological restoration propose the use of native plants, the knowledge of their physiological and ecological traits and the proper techniques which ameliorate seedling survival in adverse conditions. Priming consists of a regulated hydration in water or osmotic solutions; this permits the improvement of some metabolic processes, but prevents germination. This treatment increased seed vigor with a rapid and uniform germination and development. These advantages induce a valuable improvement on the seed response<br />for applied purposes in agriculture. Because the advantages obtained during priming are kept after seed d e hydration. Seeds develop a natural priming when they lie in the soil. During soil burial , molecular and physiological responses are induced and which are very similar to those mechanisms reported in priming. Burial and natural priming enhancing germination and emergence could have an ecological significance. Effects produced by natural priming probably were selected during the evolution of plants which forms soil<br />seed banks.</p>

scholarly journals About rats and jackfruit trees: modeling the carrying capacity of a Brazilian Atlantic Forest spiny-rat Trinomys dimidiatus (Günther, 1877) – Rodentia, Echimyidae – population with varying jackfruit tree (Artocarpus heterophyllus L.) abundances

2015 ◽  
Vol 75 (1) ◽  
pp. 208-215 ◽  
Author(s):  
JHF Mello ◽  
TP Moulton ◽  
DSL Raíces ◽  
HG Bergallo
Keyword(s):  
Mathematical Model ◽  
Population Size ◽  
Seed Production ◽  
Atlantic Forest ◽  
Small Mammal ◽  
Carrying Capacity ◽  
Real Data ◽  
Brazilian Atlantic Forest ◽  
Artocarpus Heterophyllus ◽  
Small Mammal Community

We carried out a six-year study aimed at evaluating if and how a Brazilian Atlantic Forest small mammal community responded to the presence of the invasive exotic species Artocarpus heterophyllus, the jackfruit tree. In the surroundings of Vila Dois Rios, Ilha Grande, RJ, 18 grids were established, 10 where the jackfruit tree was present and eight were it was absent. Previous results indicated that the composition and abundance of this small mammal community were altered by the presence and density of A. heterophyllus. One observed effect was the increased population size of the spiny-rat Trinomys dimidiatus within the grids where the jackfruit trees were present. Therefore we decided to create a mathematical model for this species, based on the Verhulst-Pearl logistic equation. Our objectives were i) to calculate the carrying capacity K based on real data of the involved species and the environment; ii) propose and evaluate a mathematical model to estimate the population size of T. dimidiatus based on the monthly seed production of jackfruit tree, Artocarpus heterophyllus and iii) determinate the minimum jackfruit tree seed production to maintain at least two T. dimidiatus individuals in one study grid. Our results indicated that the predicted values by the model for the carrying capacity K were significantly correlated with real data. The best fit was found considering 20~35% energy transfer efficiency between trophic levels. Within the scope of assumed premises, our model showed itself to be an adequate simulator for Trinomys dimidiatus populations where the invasive jackfruit tree is present.

scholarly journals Population size, habitat fragmentation, and the nature of adaptive variation in a stream fish

2014 ◽  
Vol 281 (1790) ◽  
pp. 20140370 ◽  
Author(s):  
Dylan J. Fraser ◽  
Paul V. Debes ◽  
Louis Bernatchez ◽  
Jeffrey A. Hutchings
Keyword(s):  
Genetic Variation ◽  
Habitat Fragmentation ◽  
Population Size ◽  
Brook Trout ◽  
Small Populations ◽  
Adaptive Genetic Variation ◽  
Genetic Population ◽  
Fragmented Populations ◽  
Large Populations ◽  
Adaptive Differentiation

Whether and how habitat fragmentation and population size jointly affect adaptive genetic variation and adaptive population differentiation are largely unexplored. Owing to pronounced genetic drift, small, fragmented populations are thought to exhibit reduced adaptive genetic variation relative to large populations. Yet fragmentation is known to increase variability within and among habitats as population size decreases. Such variability might instead favour the maintenance of adaptive polymorphisms and/or generate more variability in adaptive differentiation at smaller population size. We investigated these alternative hypotheses by analysing coding-gene, single-nucleotide polymorphisms associated with different biological functions in fragmented brook trout populations of variable sizes. Putative adaptive differentiation was greater between small and large populations or among small populations than among large populations. These trends were stronger for genetic population size measures than demographic ones and were present despite pronounced drift in small populations. Our results suggest that fragmentation affects natural selection and that the changes elicited in the adaptive genetic composition and differentiation of fragmented populations vary with population size. By generating more variable evolutionary responses, the alteration of selective pressures during habitat fragmentation may affect future population persistence independently of, and perhaps long before, the effects of demographic and genetic stochasticity are manifest.

Seed and seedling studies of three Trifolium subterraneum var. brachycalycinum lines, in a predominantly summer rainfall environment

1995 ◽  
Vol 35 (8) ◽  
pp. 1101
Author(s):  
GM Lodge
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Trifolium Subterraneum ◽  
Summer Rainfall ◽  
Sowing Time ◽  
Buried Seeds ◽  
Initial Seed ◽  
Total Seed

Field experiments were conducted in a predominantly summer rainfall environment to investigate burr burial, seed production, seed characteristics, seedling emergence and survival, and the effects of time of sowing on 3 Trifolium subterraneum var. brachycalycinum lines (cv. Clare and 2 local lines). Each line produced more surface than buried burrs; surface burrs were 59% (range 56-62%) of the total number of burrs recovered and produced 59% of the total seed number. Numbers of seeds per burr were similar for surface and buried burrs, however, buried seeds were 0.97 mg heavier (P<0.05) than surface seeds. Storage for 5 months at 25/60�C decreased hardseed content of surface seed by 50% and buried seed by 70%. Surface and buried seeds stored at 25/25�C for 3 months prior to sowing in trays had a total emergence of <10%, compared with 70% emergence for seeds stored at 25/60�C before sowing. These emergence differences reflected their levels of hardseededness. Numbers of seeds recovered from the soil were not significantly different among lines, declining from about 4200 seeds/m2 after initial seed set to 150 seeds/m2 by the following winter, a 97% decrease. Seed production in the second year increased seed reserves to about 8730 seeds/m2. With no further seed production, levels had declined by 93% in June 1990 and by 99% in May 1991. These data confirm the importance of annual seed production for persistence. Total seedling emergence in summer-autumn accounted for only 10% of the estimated seed production in each year. Seedling survival in summer-autumn 1988-89 was 92.7%, more than double the survival in 1989-90. The effect of sowing time on flowering was always significant, with time to first flower being highest (196 days) for the earliest sowing in March (P<0.05), progressively decreasing (P<0.05) to 108 days for the latest sowing in July. In March, April and May sowings, inflorescence numbers on the first day of flowering were similar at about 120/m2, but increased markedly (P<0.05) for sowing in June or July. However, for the March and July sowings, number of inflorescences at the 9 November 1990 count, were lowest (P<0.05). May or June sowings had the highest number of burrs and seeds (P<0.05), indicating that these may be the best sowing times for maximum seed production in these Trifolium subterraneum var. brachycalycinum lines.

scholarly journals Adding landscape genetics and individual traits to the ecosystem function paradigm reveals the importance of species functional breadth

2017 ◽  
Vol 114 (48) ◽  
pp. 12761-12766 ◽  
Author(s):  
Antonio R. Castilla ◽  
Nathaniel S. Pope ◽  
Megan O’Connell ◽  
María F. Rodriguez ◽  
Laurel Treviño ◽  
...  
Keyword(s):  
Gene Flow ◽  
Seed Production ◽  
Critical Role ◽  
Pollen Dispersal ◽  
Plant Size ◽  
Dispersal Ability ◽  
Floral Display ◽  
Long Distance ◽  
Pollinator Community ◽  
Local Plant

Animal pollination mediates both reproduction and gene flow for the majority of plant species across the globe. However, past functional studies have focused largely on seed production; although useful, this focus on seed set does not provide information regarding species-specific contributions to pollen-mediated gene flow. Here we quantify pollen dispersal for individual pollinator species across more than 690 ha of tropical forest. Specifically, we examine visitation, seed production, and pollen-dispersal ability for the entire pollinator community of a common tropical tree using a series of individual-based pollinator-exclusion experiments followed by molecular-based fractional paternity analyses. We investigate the effects of pollinator body size, plant size (as a proxy of floral display), local plant density, and local plant kinship on seed production and pollen-dispersal distance. Our results show that while large-bodied pollinators set more seeds per visit, small-bodied bees visited flowers more frequently and were responsible for more than 49% of all long-distance (beyond 1 km) pollen-dispersal events. Thus, despite their size, small-bodied bees play a critical role in facilitating long-distance pollen-mediated gene flow. We also found that both plant size and local plant kinship negatively impact pollen dispersal and seed production. By incorporating genetic and trait-based data into the quantification of pollination services, we highlight the diversity in ecological function mediated by pollinators, the influential role that plant and population attributes play in driving service provision, and the unexpected importance of small-bodied pollinators in the recruitment of plant genetic diversity.

scholarly journals Using Restriction Fragment Length Polymorphisms to Assess Temporal Variation and Estimate the Number of Ascospores that Initiate Epidemics in Field Populations of Mycosphaerella graminicola

2001 ◽  
Vol 91 (10) ◽  
pp. 1011-1017 ◽  
Author(s):  
J. Zhan ◽  
C. C. Mundt ◽  
B. A. McDonald
Keyword(s):  
Temporal Variation ◽  
Population Size ◽  
Effective Population Size ◽  
Restriction Fragment ◽  
Fragment Length ◽  
Mycosphaerella Graminicola ◽  
Source Population ◽  
Effective Population ◽  
Length Polymorphisms ◽  
Restriction Fragment Length

Restriction fragment length polymorphisms (RFLPs) and DNA fingerprints were used to assess temporal variation and estimate the effective population size of the wheat pathogen Mycosphaerella graminicola over a 6-year period. In each year, the fungal population was founded by ascospores originating from outside the sampled fields. A total of 605 fungal isolates were included in this study. Our results indicate that the genetic structure of these M. graminicola populations were stable over the 6-year period. The common alleles at each RFLP locus were present at similar frequencies each year. More than 99% of gene diversity was distributed within populations sampled from the same year and less than 1% was attributed to differences among years. The lack of population differentiation among collections taken in different years indicated that the effective size of the source population was sufficiently large that genetic drift was insignificant in this location. It also suggests that the initial colonists from ascospore founder populations were a fair reflection of the source population. We estimate that the effective sizes of these field populations ranged from 3,400 to 700,000 individuals, depending on the size of the field sampled and assumptions about mutation rates. Estimates of the number of ascospores initiating epidemics of leaf blotch disease in each field plot and factors that contribute to the large effective population size of M. graminicola are discussed.

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