Bok Tower Gardens Rare Plant Conservation Program
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Mission: to understand and preserve the rare plants of Florida Microhabitat studies inform management needs for two endangered central Florida scrub species, Dicerandra immaculata var. immaculata and Lupinus aridorum Lakela’s mint Scrub lupine Ridge species are particularly unique & found nowhere else in the world Archbold biological station Lakela’s Mint and Scrub Lupine are each: • located on specific ridge systems • restricted to scrub habitat • very narrow geographic distribution within ridge/habitat • Short-lived perennials • Habitats historically maintained by frequent burns • primarily threatened by loss of and degraded habitat due to fire suppression • Remaining natural populations declining • Nearly all remaining populations on private land • Federally and state listed as endangered • Population introductions likely necessary to prevent extinction Goals for microhabitat research: • characterize specific habitat requirements required for survival and recruitment • data to inform land managers • inform population introductions Lakela’s Mint (Dicerandra immaculata) • 5 wild (historical) meta- populations (1 large population fragmented by development) – 1 has been augmented – 2 sites have large areas where individuals were extirpated due to habitat degradation • 3 introduced populations Lakela’s Mint D. immaculata var. immaculata Evaluating microhabitat parameters Data collection in September 2012 from seven populations: three introduced, one augmented and three natural 20 healthy plants and 20 random locations (without plants) were chosen 20 extirpated locations at two wild sites Data collection occurred in within 1 meter diameter areas and 1 m2 quadrats around each plant or random/extirpated location Investigation differences between: 1. Wild plants versus random locations 2. Wild plants versus extirpated areas 3. Wild versus introduced plants Habitat characteristics 1. distance to the nearest overstory tree (& species) 2. distance to the nearest woody shrub (& species) 3. number of woody stems within a 1 m radius 4. number of plant species within a 1 m radius 5. number of mints within a 1 m radius 6. maximum height of the understory vegetation within a 1 m radius; 7. average depth of detritus in a 1 m2 quadrat (& type) 8. relative abundance of ground cover types within a 1 m2 1. bare ground 2. detritus 3. grasses 4. herbaceous plants (non-grasses) 5. woody plants 9. canopy density 10. soil moisture ©Cheryl Peterson Overall results Versus random locations, wild plants associated with… – shorter understory vegetation – less detritus (type matters) – fewer woody stems – greater numbers of conspecifics – less canopy coverage Introduced locations were more similar to random locations than wild locations – realized niche may be narrower than fundamental Extirpated: bare ground decreased, soil moisture increased, diversity of shrubs decreased (mostly were dense thickets of runner oaks), and composition of the overstory changed Can you see Trina….? Lakela’s Mint Summary: • Grows in open, sunny habitat (i.e., “gap specialist”) • Often hugged treeline: filtered sunlight optimum during drought • bare sand essential for recruitment Primary threats: • Competition from invasives – Brazilian pepper – allelopathic – dodder/love vine - parasitic – Grasses outcompete plants • Runner oaks – will eliminate habitat quickly Scrub Lupine - Lupinus aridorum McFarlin ex Beckner (Fabaceae) Photo by Brad Kolhoff Richardson, Rynear, Peterson. 2014. Microhabitat of Critically Endangered Lupinus aridorum (Fabaceae) at Wild and Introduced Locations in Florida Scrub Plant Ecol (2014) 215:399–410 Rare Plant Conservation Program Dr. Matthew Richardson L. aridorum L. diffusus Scrub lupine microhabitat study 1. Multiple cytotypes? (can influence distribution) 2. Characterize habitat between natural and random locations 3. Characterize habitat between natural and introduced plant locations 45 EORs 9 (2014) Natural populations (1-300 individuals) – all declining Introduced (25-475) – some successful, some less so Photo: Cheryl Peterson Cytotypes – methods and results • Leaf samples from 10 individuals at each of three populations (most genetically diverse, Bupp 2013) • Flow cytometry done at Iowa State University • Controls – two standards of L. villosus (diploid: Conterato and Schifino-Wittman 2006) • All L. aridorum tested were diploid. – Six sites, 3 introduced populations, 3 wild – 60 wild locations, 60 introduced, 100 random – Environmental measurements • Distance to nearest overstory tree • Distance to nearest shrub • Soil moisture • % of bare ground within 2 m2 quadrat • % detritus (six classifications) • % grasses • % herbaceous • % woody plants • Canopy density • # woody stems • # species (and predominant species id) • Maximum height of understory Main findings • Wild L. aridorum grew closer to trees and shrubs – just close enough to be partially shaded, • Lower soil mosture, • grew with a greater mixture of detritis than randomly expected. • Wild L. aridorum associated with Persea borbonia and S. repens more often than random; wild locations more associated with natives than random or introduced. • Introduced locations quite different than wild. More similar to random locations (habitat preferences not known at the time of planting) • Introduced plants have survived and recruited in a broader niche than wild plan locations. Comparison of findings: Lakela’s Mint Scrub Lupine • Gap specialist • May not be a gap specialist due • Maintaining canopy gaps and to its positive association with sufficient sand gaps necessary trees, shrubs and detritus. • Filtered sunlight (treeline • Distance to nearest shrubs/trees areas) important for stressful important times • Specific associates seem to be • Type of associates not critical important • % detritus most important • Mix of detritus most important • Soil moisture not significant • Soil moisture important • Fundamental niche may be • Same: introduced plants have wider than realized (clumped survived and recruited in a distribution of recruits) broader niche than wild plant locations Scrub Lupine - Management implications • Manage carefully around existing plants (cannot take root or as much plant disturbance) • Intense manage acceptable to increase population area (may expose seed bank) • Prescribed fire (seed bank will allow species to persist) • Consider mgmt for blackspot and other diseases - removing overgrowth of grapevine important • Keep associates & diversity (below- ground dynamics may be crucial) • Remove invasive grasses • Maintain soil health/profile (much of plant dynamics may be below ground) Lakela’s Mint - Management implications • Can take minor disturbance, but much of population should be untouched at any one time (preserve adults - no seed bank) • No roller-chopping • ONGOING, LITTLE-AT-A-TIME HAND- MANAGEMENT NECESSARY for existing populations • Big, high impact management event will destroy existing population status • Hickory and sand pines positive • Gradual hand-removal of oaks and invasive plant species • Apply herbicide treatment to stems (esp. runner oaks!) or problem will soon get worse (dense oak thickets) • Hand-weeding & small shrub/tree removal, detritus raking • Mini-burns should be explored Current related research Lakela’s Mint Scrub Lupine • Demography – PVA on eight • Soil symbiont years census data (hand characterization (rhizobia & management history included) mycorrhizae) • Seed biology • Root exudates (metabolomics) – Short-lived seed bank (1 yr) • – in situ influences on Population genetics recruitment and survival • introductions • Pollinators • Demography • Mating system • Seed biology • Seed predators – Long-lived seed bank (+20 yrs) Seed treatments to better understand in situ recruitment Liquid smoke stimulates germination, oak leachate prevents it Bombyliid fly (Bombylius mexicanus) Lakela’s Mint: Honey bee (Aphis mellifera) Pollinator observations • Three in situ populations (HF, HBP, IS) • two years of data during flowering 2012 & 2014 • Timed observations & counts of floral visitations • Comparisons of behavior of native and non-native visitors within one plant • Results: >93% pollinators are non-native honeybees, 7% are native pollinators (bumblebees, butterflies, moths, flies, and a wasp) • Honeybees visit plants… – in sunny habitat – with large floral displays • Native pollinators visit plants… – Mostly in sun, but also in shade – with large floral displays, but not as significantly • Implications = fewer individuals contributing to next generations • Also - honeybees visit many more flowers within a plant than natives. – May promote selfing Mating system success of selfing versus outcrossing • 12 plants in the Collection beds • open pollination control • Pollinator excluded • Anther-removal • Selfed (within plant, not w/in flower) • Crossed • 10 am – 2 pm, Oct 3rd - 29th, 2013 B=racemes bagged before flower buds opened; Average number of seeds/calyx:=0.7 C=anthers removed as flowers opened; (low 0.2, High 1.44) D=selfed (same plant): E=outcrossed (different plant). Seed production: crossing twice as successful Controls=flowers open-pollinated. as selfing C, D, E, and controls-8 flower buds per raceme, Not done here - # of intact seeds (up to 96% all other buds excised. empty, based on several previous ex situ counts) Seed predators • 2013 & 2014 within two populations – Two populations have slightly different management histories – Bagged 10 racemes per each of four seed-development stages A. Flowering is just finishing up (some petals or