IMPACT OF RECENT FIRE ON TRAP NESTING BEES IN

LONGLEAF PINE UPLANDSSara McDonaldThesis Proposal

Fall 2015

INTRODUCTIONBackground on longleaf pine, fire management,

and ecology of trap-nesting bees

The question: do early-season fires negatively impact solitary native bees that nest aboveground?■ Upland longleaf pine forests are fire-dependent ecosystems;

prescribed burning is a necessary tool for biodiversity management and wildfire prevention

■ Prescribed burning is implemented based on conservation priorities. Sandy Hollow WMA conservation priority is quail, gopher tortoise.

■ How do these burn regimes impact non-target organisms?■ Trap nesting bees have sensitive ecologies, require a balance between

floral resources and nesting materials■ Fire may increase floral diversity depending on frequency, but may

reduce or eliminate suitable nesting materials■ At what scale and burn frequencies are negative impacts on seen?

Native bees as a conservation priorityIncreased interest in pollinators, USDA initiatives

Louisiana Department of Wildlife and Fisheries has no invertebrate conservation plan

Pollinators, particularly native bees, would be a great candidate because of popular interest

Important in natural and agricultural ecosystems

Introduction to longleaf pine ecosystems

Longleaf pine dominates canopy, wiregrass and forbs in the understory, very high plant diversity with over 300 rare and endangered plant species, over 1000 total species

1-3 year burn frequency

Declining ecosystems in the southeast, approximately 3% of historic range mostly in managed tracts

Burn mosaics

Mosaic complexity: frequency, intensity, burn extent, season, multiple scales

Prescribed for: habitat type, conservation goals

Can also apply to natural fire regimes, wildfire, but typically burn mosaics (pyrodiversity) are a management goal; programs well-developed especially in Australia, South Africa (Parr and Andersen 2006)

Need empirical support to reduce detrimental impacts (fragmentation)

MODIS imagery, landscape level burn scars

Fire as a management toolShrubby understory, less frequent burn, rapid recovery from fire Grassy understory from frequent burning

Local scale heterogeneity, woody vegetation density, intensity variation, local burn history

Variability in size and material attract different species

Megachilids nest in woody stems Completed nest plugs

Trap nesting beesTrap nests are simple to construct

Attract solitary native bees that nest aboveground in hollow stems, 15-20 species can be collected with just 20 traps (Tscharntke 1998)

Provide community data; habitat complexity and community stability (Ebeling et. al 2012)

• Brood cell density (abundance)

• Brood parasitism (trophic interactions)

Nest construction Taxonomy can be determined by nest plug composition, brood cell construction

Different species have different flight windows and nesting seasons – early, mid, late; univoltine, bivoltine, multivoltine

Brood parasites (cleptoparasites) invade brood cells and lay eggs; steal provisions, some obligate parasites; host-specific

Brood Cells

Example brood cells, linear arrangement, lengthwise in hollow stem, Osmia lignaria (Blue Orchard Bees)

Abundance can be determined by counting brood cells, survival (emerged adults)

Parasitism identified by dissecting nests; parasitism rates (around 13% - Ebeling et. al 2012)

PROPOSED PROJECTSite identification, trapping methods, expected outcomes

Sampling Objectives, Methods

■ Transects measured 50m, 200m, and 350m from comparison sites (burn v. unburned) or

■ % completely burned within 300m radius

■ 6 replicates at each distance (or %), 18 traps per burned site, 18 traps unburned

■ Include pitfall sampling for different invert community data (ground dwelling arthropods) and blue vane trapping for earlier data; adult, non-Apis bees

Solitary bee foraging distance from nest approx. 300m Community abundance, similarity comparisons between burned, unburned sites along a gradient

Specimen collection and processingEmergence in labFreeze, wash, sortPinning and dry storageVials with ethanol

PROJECT SCHEDULEChronology

Project Timeline■ December –

February 2016- Materials set up, identify sampling sites

■ February 2016- Set up trap nests, blue vane traps and pitfall traps to begin collecting specimens.

■ November, 2016- Remove all traps from the field.

■ Feb, 2017 – Anticipated emergence of trap nesting bees into emergence chambers.

■ March-June 2017- Data analysis and reporting.

February 2016 to November 2016- Trapping (see table). Sort collected specimens according to species.

  Week 1 Week 2 Week 3 Week 4 Week 5 Week 6…

Trap nests Monitor - - Monitor - -

Pitfall Set Collect - Set Collect -

Blue vane Set Collect - set Collect -

Table 1 - Example collection timeframe for three trap types over a 6 week period. Pitfall and blue vane traps are set at the beginning of Weeks 1 and 4. The traps will be collected at the beginning of Weeks 2 and 5. Over this 6 week time period, there will be two 7-day collection periods, which will continue on this schedule from week 7 through the end of the project. Trap nests will be monitored every 3 weeks for nesting activity or disturbance.

ReferencesEbeling A, Klein A-M, Weisser WW, Tscharntke T (2012) Multitrophic effects of experimental changes in plant diversity on cavity-nesting bees, wasps, and their parasitoids. Oecologia 169:453–465. doi: 10.1007/s00442-011-2205-8

Parr CL, Andersen AN (2006) Patch Mosaic Burning for Biodiversity Conservation: a Critique of the Pyrodiversity Paradigm. Conserv Biol 20:1610–1619. doi: 10.1111/j.1523-1739.2006.00492.x

Tscharntke T, Gathmann A, Steffan-Dewenter I (1998) Bioindication using trap-nesting bees and wasps and their natural enemies: community structure and interactions. J Appl Ecol 35:708–719. doi: 10.1046/j.1365-2664.1998.355343.x