[Pollinator] USGS Release: Picky Pollinators: Native Bees Selective About Where to Live & Feed (It's Pollinator Week)

[Catherine E Puckett]

This release can be found in the USGS Newsroom at: 
http://www.usgs.gov/newsroom/article.asp?ID=2833.


News Release



June 21, 2011 


Ralph Grundel 
219-926-8336 x422 
rgrundel at usgs.gov 
Catherine Puckett 
352-264-3532 
cpuckett at usgs.gov 
Marisa Lubeck 
303-202-4765 
mlubeck at usgs.gov 




Picky Pollinators
Native Bees are Selective about Where They Live and Feed


Note to Editors: It?s National Pollinator Week, June 20-26
INDIANA DUNES NATIONAL LAKESHORE, Ind. ? Native bees ? often small, 
stingless, solitary and unnoticed in the flashier world of stinging 
honeybees ? are quite discriminating about where they live, according to 
U.S. Geological Survey research.
The study found that, overall, composition of a plant community is a weak 
predictor of the composition of a bee community, which may seem 
counterintuitive at first, said USGS scientist and study lead Ralph 
Grundel. This may be because specialized plant-bee interactions, in which 
a given bee species only pollinates one plant species and that plant 
species is only pollinated by that bee species are not common.  More 
common is for a plant species to be pollinated by many pollinator species 
and each pollinator species pollinating many species of plants.
Given this complex network of interaction between plants and their 
pollinators, it is not surprising that knowing which plants occur in an 
area does not necessarily allow us to predict which bees will occur in 
that area, Grundel said.
Unraveling such mysteries surrounding how native bees inhabit and use 
different habitats is especially essential now -- the National Academy of 
Sciences has reported that not only is there direct evidence for decline 
of some pollinator species in North America, but also very little is known 
about the status and health of most of the world's wild pollinators. Yet 
without them, the ability of agricultural crops and wild plants to produce 
food products and seeds is jeopardized.
"The issues facing honeybees introduced pollinators whose populations are 
spiraling downward, means that it is even more vital to understand the 
role of native bees as pollinators and how they divide up and use a 
landscape," said Grundel.
Many studies have been conducted to determine how a variety of animals ? 
birds, mammals, and reptiles, for example ? use their native landscapes, 
but few such studies have been undertaken for native bees.  ?That?s why 
this type of study is fundamental for enhancing our understanding of 
native bee distribution,? Grundel said. ?Our research findings clearly 
reveal that maintenance of a diverse and abundant bee community requires 
that managers consider a suite of local and landscape characteristics and 
management actions.?
Grundel and his colleagues wanted to find out if the kinds of plants that 
live in different habitats can predict what kinds of bees will be there or 
if other factors ? such as soil type, tree density or even fire -- are 
more important. To do this, the team surveyed landscapes and collected and 
identified nearly 5,000 native bees representing at least 175 species in 
five kinds of habitats at Indiana Dunes National Lakeshore and nearby 
natural areas around northwestern Indiana. These habitats ranged from 
dense forests to open fields.
"We had suspected that the closer our collecting sites were to each other 
the more similar the bees communities we found would be ? but we were 
wrong," Grundel said. "In fact, mere physical proximity wasn't a very good 
predictor of how similar bee communities at different sites would be to 
each other. Instead, local factors ? and even the micro-habitats that we 
often ignore ? are really important in determining what kinds of bees use 
an area."
Because many native bees are ground- and cavity-nesters, the scientists 
weren?t surprised to find that an abundant supply of dead wood, such as 
woody debris and dead tree limbs, was essential in determining what kinds 
of bees lived where. They were surprised, however, at how important other 
factors were, including bee preferences for specific soil characteristics 
and for areas that had burned in the previous two years.
Bee abundance ? how many bees were captured at a site ? was lower in areas 
with a dense tree canopy and higher if a fire had occurred recently in the 
area. Bee diversity ? the number of different kinds of bees ? was higher 
in areas with less tree canopy, but with a higher diversity of flowering 
plants and an abundance of nesting resources, such as woody debris.
The presence of suitable nesting material was at least as important in 
determining how many types of bees might use a site as was diversity of 
plants, which provide nectar and pollen to the bees. The composition of an 
entire bee community was linked to higher plant variety, less canopy cover 
and soil characteristics that may be best-suited for nesting.
The study found that specialist bees ? those picky native bees that gather 
pollen from only a few kinds of plants ? were more likely to live in open 
areas than areas with a higher density of trees.
"Specialist bees, not surprisingly, were also more associated with the 
presence of native plants in the areas, but a lot of these native plants 
were more likely to occur in disturbed areas, including areas that had 
recently been burned and, somewhat to our surprise, residential areas 
where soil disturbance is commonplace," Grundel said.
However, specialist bees were often rarer and mainly used open habitats, 
such as grasslands and savannas.  According to a 2005 study, said Grundel, 
such open Midwest habitats are today perhaps the most poorly conserved 
habitats on the planet, causing concern about long-term conservation of 
such bee species.
"At several locations around the world, specialist bumblebees living in 
plant rich areas, such as these open habitats, have declined 
significantly," Grundel said.  "Similar bumblebee declines have been 
documented in the Midwest U.S. Documenting how diet breadth, rarity and 
habitat use are related is important for understanding such patterns of 
decline and was one of the main objectives of our study. We collected six 
bumblebee species in our study while a 1930s study in this area collected 
twelve species. Four of the species we did not find in our study have been 
identified as bumblebees of special concern due to their disappearance 
from sites across the Midwest."
USGS researchers in Indiana and Maryland are following up on this research 
with a recently initiated study examining how native bee populations 
across the national park system might be affected by climatic variation.
The paper, Floral and nesting resources, habitat structure, and fire 
influence bee distribution across an open-forest gradient, was published 
in Ecological Applications and may be read online.  Primary authors are 
Ralph Grundel, USGS; Robert Jean, Indiana State University; and Krystalynn 
Frohnapple and Noel Pavlovic, USGS.
 
Photos for this release:
Visit: http://gallery.usgs.gov/tags/NR2011_06_21 for all available photos. 


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###

 
~~~~~~~~~~~~~~~~~
Catherine Puckett 
USGS Office of Communications
2201 NW 40th Terrace
Gainesville, FL 32605-3574
OFFICE PHONE: 352-264-3532
NEW CELL PHONE: 352-278-0165
FAX: 352-374-8080
EMAIL: cpuckett at usgs.gov
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