? Other biological threats

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1 Potential consequences of small size & habitat fragmentation on Eastern Prairie ringed Orchid (Platanthera leucophaea) populations Recovery Needs for P. leucophaea Manage for population persistence Status and management of pollinators Population restoration Protection against anthropogenic factors Department of Biology University of South Dakota Platanthera leucophaea Eastern prairie fringed orchid Talk Outline I. Ecology of P. leucophaea II. Genetics & rarity III. Reproductive biology & rarity IV. Management trends Historical & current distribution of P. leucophaea in the U.S. Exotic species Loss of habitat 9 Reed Canary Grass Purple Loosestrife Threats to Prairie ringed Orchids Extinct populations Extant populations Overcollecting? Other biological threats Life cycle of P. leucophaea P. leucophaea and its pollinators Wind, Water, Earthworms?? Seed dispersal Dormancy Sexual reproduction Germination & establishment Perenniality Competition Colonization of new populations Adapted from Bowles, 983 Photos from USWS image library. January 7, 5

2 Sexual reproduction Adapted from Bowles, 983 Life cycle of P. leucophaea Seed dispersal Perenniality Wind, Water, Earthworms?? Dormancy Germination & establishment Competition Colonization of new populations % infected embryos Soil moisture soil ph Nov Jan Mar May June July Sept Seed germination at Pickerel Creek Lightinhibited Waterinduced Stimulated by burning Mycorrhizaedependent Stage Germination (%) Stratification Period and Seed Source Effects on Seed Germination Abbott Wadsworth Lyons Seed Source Pooled No stratification 8 weeks stratification 6 weeks stratification Bowles et al., Mean % Stage Germination Treatment and Seed Age Effect on Germination Treatment Inoculated Inoculated/ stratified Stratified 8 mos. 6 mos. Seed Age Bowles et al., Sexual reproduction Adapted from Bowles, 983 Life cycle of P. leucophaea Seed dispersal Perenniality Wind, Water, Earthworms?? Dormancy Germination & establishment Competition Colonization of new populations Status of tagged plants in Pickerel Creek Population, = flowering plant N = vegetative plant = no plant seen Grazed = grazed by deer = no data collected Data from J. Windus, Ohio Dept. of ish & Wildlife Plant N 993 N N 994 N N N 995 N N N N N N N 996 N N N N N January 7, 5

3 Number of lowering Plants Population sizes in Ohio, Year Sporadic flowering may be related to: Soil moisture Lake levels Annual precipitation Burning Data from J. Windus, Ohio Dept. of ish & Wildlife No. of lowering Plants Killbuck Wildlife Area Inches of precipitation relative to average conditions Year Data from J. Windus, Ohio Dept. of ish & Wildlife No. of lowering Plants Pickerel Creek Wildlife Area No data Average level of Lake Erie (m) II. Genetics & Rarity in P. leucophaea How much genetic variation, estimated with neutral molecular markers, is detectable in eastern populations of P. leucophaea? Are the levels and structure of genetic variation comparable to western populations of the species? Is there evidence of fragmentation or small population size in molecular genetic variation? Year Data from J. Windus, Ohio Dept. of ish & Wildlife P. leucophaea populations surveyed for genetic variation Populations surveyed with RAPD s Populations surveyed with allozymes & RAPD s pops. 3 pops. Gene Diversity Genetic Diversity Compared at Allozyme and RAPD Loci % Polymorphic Loci OH MI ME OH MI ME 9 allozymes loci; 7 RAPD primers 63 bands Allozymes RAPD's Allozyme data are lacking for Michigan & Maine pops. January 7, 5 3

4 % Differentiation among populations How genetically distinct are populations of P. leucophaea? A comparison across species & markers P. leucophaea,,,3 P. integrilabia 4,3 P. ciliaris 3 P. blephariglottis 3 Other orchids 5 ISSR s RAPD s Allozymes Index of genetic variation Population Size vs. Diversity at RAPD Loci log harmonic mean population size % Polymorphic Loci r =.9; P >.5 Gene diversity r =.7; P >.5 4. Wallace, ; Havens and Buerkle, 999; 3 Cowden, 993; 4 Birchenko, ; 5 Case, Geographic Distance (km) Genetic vs. Geographic Distances Genetic Distance from RAPD s Conclusions Genetic Variation in P. leucophaea Allozymes and RAPD s suggest different levels of genetic diversity in P. leucophaea. Allozyme & RAPD loci follow different evolutionary trajectories Both data sets also detected significant structure among populations. Is this a consequence of its current rarity or an indication of its ancestry? Population structure Loss of alleles due to genetic drift and/or fixation of alleles in isolation Population history ounder effects and associated loss of diversity Origin from divergent source populations and fixation of alleles Maine population excluded; r =.467; P >.5; Mantel test Is reduced genetic variation likely to lead to population extinction? Are these results useful to the preservation of this species? Yes, they are useful because They demonstrate the importance of using multiple criteria to judge the worthiness of populations for preservation. The finding that diversity is not correlated with population size is, perhaps, a positive indication that genetic diversity can be maintained in smaller populations. The identification of genotypic patterns provides a baseline for managers, should they wish to experimentally augment populations. January 7, 5 4

5 Inbreeding in Ohio populations ing & inbreeding in P. leucophaea Nonrandom mating Random mating Nonrandom mating A B C D E G Sampled N = IS (allozymes) Population ~ 4 sec S. Datwyler ing is promoted by: Sequential opening of flowers Delayed bending of pollinaria Pollinator behavior Inbreeding depression in offspring Inbreeding is possible through: Geitonogamy Mating between closely related genets III. Reproductive Biology of P. leucophaea Sites Pickerel Creek Wildlife Area (large N, high IS ), repeated Killbuck Wildlife Area (small N, low IS ), repeated Pollination treatments No pollination Variables Relative seed weight PC KB Percent Pickerel Creek Capsules recovered ruit Production p <.5 for all years; Gtest of Independence on seed set Percent Capsules recovered Killbuck 999 p >.5 for both years; Gtest of Independence on seed set Seed viability X Reproductive success at Pickerel Creek Reproductive success at Killbuck OutX 998 a a b.8.8 a b c NS a b b.. N = Relative Seed Weight % Seed Viability Relative Seed Weight % Seed Viability Significant differences (p <.5) in Bonferroni tests are indicated by unlike symbols. OutX N = Relative Seed Weight % Seed Viability Relative Seed Weight % Seed Viability No significant differences in KruskalWallis tests were found among treatments. January 7, 5 5

6 Inbreeding Depression Compared Across Estimators Mean % Viable Seeds (*) Crossing Effect on Percent Seed Viability Population Cross Between Within 3 4 Seed Source Bowles et al., Population, year Pickerel, 998 Pickerel, Killbuck, 999 Killbuck, ing angiosperms ing angiosperms IBD = (outcross self)/outcross..6 Seed production.3.9 Relative seed mass Seed germination.4.5 Percentage of viable seeds Overall.3.53 Husband & Schemske, 996 Conclusions Inbreeding depression Is inbreeding depression a significant threat to this species? Early acting inbreeding depression is possible in P. leucophaea, although the magnitude of IBD can vary temporally and across populations. Higher levels of seed set among openpollinated capsules at Pickerel Creek compared to Killbuck suggest that smaller populations may be pollinatorlimited. Geitonogamy and matings between related genets allow for inbreeding. Allozyme data suggest that inbreeding happens. ing is likely to lead to fewer viable seeds. So, inbreeding depression could negatively impact populations, but.. Each flower is capable of producing thousands of seeds, some of which will likely be viable. Exotic Species Reed Canary Grass Threats to Prairie ringed Orchids Overcollecting Purple Loosestrife Inbreeding Limited Reproductive Potential Loss of Habitat Pollinator behavior IV. Current Management Trends Preserve habitat and size of extant populations Maintain natural hydrologic cycles and removal of drainage tiles Shrub and invasive species removal by cutting, herbicides, fire Maintain habitats that are ecologically diverse to allow orchids to retreat during years of high lake levels Use of fire to promote flowering Handpollination of plants Restoration in protected prairie remnants Ongoing demographic monitoring Continued research Demographic costs of handpollination Potential for outbreeding depression Measures to control invasive species with minimal harm to the orchids Seed germination and survival within populations January 7, 5 6

7 Similarities Evolutionary history Habit Method of reproduction Environmental threats Habitat requirements (i.e., need for periodic disturbance) Differences Narrow endemism of Piperia yadonii Different ecological niches Population sizes vs. number and distribution of populations Platanthera leucophaea Piperia yadonii ACKNOWLEDGMENTS unding Ohio Department of Natural Resources The Nature Conservancy, Ohio Chapter Ohio State University, Janice Beatley Award ield and lab assistance Daniel Crawford David Cuthrell Shannon Datwyler Kayri Havens Phyllis Higman Michael Penskar Kyle Stockwell Jennifer Windus ODNR Division of Wildlife Managers at Pickerel Creek WA & Killbuck WA January 7, 5 7