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Fragmentation & Reproductive Output. Altered landscapes Less habitat Smaller patches Various shapes Smaller populations Fewer mates Fewer resources for.

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Presentation on theme: "Fragmentation & Reproductive Output. Altered landscapes Less habitat Smaller patches Various shapes Smaller populations Fewer mates Fewer resources for."— Presentation transcript:

1 Fragmentation & Reproductive Output

2 Altered landscapes Less habitat Smaller patches Various shapes Smaller populations Fewer mates Fewer resources for pollinators Increased isolation between patches Limits exchange of genes (pollen and seed) Changes to habitat “health” Above and below ground (resources)

3 Pre-European Vegetation Source: National Land & Water Resources Audit

4 Current Vegetation Patterns (2001) Source: National Land & Water Resources Audit >5% natural vegetation

5 Reproduction Many species rely on pollen movement to generated seed Successful sexual reproduction Ensures the next generation Seed is a dispersal mechanism Maintains heterozygosity and fitness Generates new genetic combinations Seed can be an important food source for associated animals and insects – some of which will also be pollinators Fragmentation is altering important relationships within communities

6 Fragmented Landscapes

7 Less long distance gene flow

8 Fragmented Landscapes Increased within-patch matings

9 Reproductive Consequences of Fragmentation Case studies

10 Genetic erosion in Rutidosis leptorrhyncoides Herbaceous perennial Self-incompatible – S-alleles Insect pollinated Once widespread, now extremely rare Subject to severe habitat loss Small populations (<200 plants) poor reproductive performance

11 Flower Synchrony? Pollinator Availability? Week No. open flowers

12 Self-incompatibility – large population S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S 10 Genotype 66% successful seed set

13 S1S2S3S4S5S6S1S2S3S4S5S6 Genotype Self-incompatibility – small population 17% successful seed set

14 S-alleles and seed set Population size S-alleles R 2 =0.82, p= S-alleles Seed set per floret R 2 =0.68, p=0.014

15 Implications for R. leptorrhynchoides seed crops Seed crops from small populations: Few S alleles Skewed population sample Populations re-established using these seed crops have: Limited cross-compatibility Poor fecundity Low demographic viability Poor long-term persistence

16 Inbreeding depression in Swainsona recta Perennial grassland herb Longevity <20 years Insect-pollinated and gravity-dispersed Populations 10 – 400 plants Self-compatible Seed set maintained in small populations

17 Self-compatibility – large population Genotype 100% successful seed set

18 Genotype Self-compatibility – small population 100% successful seed set

19 Genetic diversity Allelic richness significantly lower in smaller populations Allelic richness of rare alleles significantly lower in smaller populations Significantly higher F is values in smaller populations Does inbreeding affect fitness?

20 Fitness Leaf Area – significantly smaller in more inbred population Dry weights - significantly lower in more inbred population

21 Fitness F is

22 Inbreeding depression in S. recta For self-compatible plants such as this inbreeding represents an important fitness constraint on long term population persistence Other considerations Utility of this seed for restoration? Importance of conserving highly inbred populations

23 Acacia acinacea Broad range across southern Australia Self-incompatible Important nitrogen fixer Key restoration species Mid-storey structural complexity Habitat & resources for other organisms Population size is not always a good predictor

24 Acacia acinacea PILOT STUDY 3 remnant populations (small, medium, large) -Open-pollinated seed families -10 progeny from 15 mothers from each population Compare seed & seedlings for: -Seed production -Seed weight -Germination -Inbreeding -Growth & survivorship

25 Seed production Filled seed Seed wt PopSize pod -1 (se) (g) (se) D (large) (±0.28) ab 0.40 (±0.02) b E (medium) (±0.36) a 0.30 (±0.01) a B (small) (±0.18) b 0.52 (±0.02) c

26 Final % Pop Germination (se) Survival (se) D (large)54.4 b (2.7)89.3 b (3.2) E (medium)40.5 a (5.1) 73.8 a (6.7) B (small)43.7 ab (2.2) 89.9 b (2.4) Germination and survival

27 Growth Sqrt Sqrt Sqrt Sqrt Pop HtSht wtRt wtSht:Rt D (large) 3.13 a b b a E (medium) 2.96 a a a a B (small) 3.21 a b b a D B E

28 Pop Outcrossing Biparental Correlated inbreedingpaternity D (large) E (medium) B (small) Inbreeding

29 Small-medium sized populations: considerably fewer fathers contributing to pollen pool These dads are genetically compatible but may not necessarily be the ‘fittest’ dads. In large populations high overall reproduction compensates for the loss of these poor seedlings over time. In small populations, there is less flexibility to compensate for poor progeny being produced.

30 Mixed mating systems Many temperate species have a mixed mating system Response to fragmentation can be population specific, but most shifts move from outcrossing to selfing Elevated inbreeding Loss of genetic diversity Selfing Outcrossing Fragmentation

31 Combined genetic and ecological study Two biomes – Western Australia & southeastern Australia 2-3 species each biome Differing life-histories Longevity Reproductive strategy Pollinators Compared genetic diversity to Population size Isolation Reproductive Output in Fragmented Common Species

32 Multiple Biomes and Species Western Australia South-eastern Australia Grasslands, grassy woodlands Open canopy woodlands Shrublands, woodlands Open canopy woodlands

33 Polymorphic loci - Western Australia Eucalyptus wandoo Tree Wind/gravity dispersal >40 yrs Insect/bird pollinated Mixed-mating Smaller populations have lower P (p<0.05) Calothamnus quadrifidus Shrub Gravity dispersal >100 yrs Bird/mammal pollinated Mixed-mating Smaller populations have lower P (p<0.05) Young et al. 2005

34 Polymorphic loci - Eastern Australia Acacia dealbata Tree Bird/insect/gravity dispersal >20 yrs Insect pollinated Self-incompatible Smaller populations have lower P (p<0.05)

35 Seed set- Western Australia Eucalyptus wandoo Tree Wind/gravity dispersal >40 yrs Insect/bird pollinated Mixed-mating Smaller populations set less seed (p<0.05) Calothamnus quadrifidus Shrub Gravity dispersal >100 yrs Bird/mammal pollinated Mixed-mating Smaller populations set less seed (p<0.001) Young et al. 2005

36 Seed set- Eastern Australia Acacia dealbata Tree Bird/insect/gravity dispersal >20 yrs Insect pollinated Self-incompatible No effect for population size

37 Fitness - Western Australia Eucalyptus wandoo Tree Wind/gravity dispersal >40 yrs Insect/bird pollinated Mixed-mating No effect for population size Calothamnus quadrifidus Shrub Gravity dispersal >100 yrs Bird/mammal pollinated Mixed-mating No effect for population size Young et al. 2005

38 Fitness - Eastern Australia Acacia dealbata Tree Bird/insect/gravity dispersal >20 yrs Insect pollinated Self-incompatible No effect for population size

39 Outcomes Common species are negatively responding to fragmentation Responses are species-specific – need to study more species Population size in an important component of this response Reduced pollination service Increased levels of inbreeding Lower seed set Suggests that perhaps we should now be concentrating on ensuring the long-term population persistence of common species Common species underpin community structure

40 Questions???


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