Sky Island research in Southern Arizona began with beetles

Couple's book covers natural history of Catalina Mountains
2013-08-11T00:00:00Z 2014-07-22T11:14:47Z Sky Island research in Southern Arizona began with beetlesTom Beal Arizona Daily Star Arizona Daily Star
August 11, 2013 12:00 am  • 

When entomologist Wendy Moore first began her research in the Santa Catalina Mountains, she tended to think of the magnificent Sky Island setting as "all just beetle habitat."

But you can't study beetles and other bugs without studying the ecosystem in which they live.

Three years later, she's not just writing about the bugs she found, but the plants and the climate and the entire natural history of the place.

She and husband, Richard Brusca, former executive director of the Arizona-Sonora Desert Museum, have written "A Natural History of the Santa Catalina Mountains" and also joined with botanists and climatologists on a research paper documenting the movement of vegetation on the mountain in response to changes in climate over the past 49 years.

For Moore, though, it all began with arthropods -segmented animals with six legs or more, such as ants, beetles and spiders.

They are intimately involved with everything else on the mountain.

Insects pollinate plants, digest leaf litter, recycle nutrients, aerate soil and provide a food supply for reptiles, birds and mammals.

They are abundant on the mountain, but not well studied.

"Despite their ecological importance, arthropods are poorly known because most are small, live in opaque habitats where observation is difficult, and few taxonomists have specialized in these groups in the Sky Island region," Moore wrote in a research paper that introduced the work of the Sky Island Arthropod Project.

Moore is something of a beetle maniac and a specialist in the "Trojan horse" of the beetle world, a critter whose fused antennae harbor a chemical factory that produces aromas irresistible to ants. The ants carry the beetles to their nests, the beetles feast on the ants, lay eggs in the nest and let the ants raise their offspring.

It works well for the beetles, but Moore is still trying to puzzle out what the ants get from the relationship.

She has done extensive field work on the carabid beetle subfamily Paussinae in Africa and Australia and she is planning field work in Sri Lanka and India.

When she was promoted to assistant professor of entomology at the University of Arizona in 2010, Moore figured she needed a second major research project on bugs closer to home, so she and her graduate students started the Arizona Sky Island Arthropod Project to discover what critters inhabit our nearby mountains.

Her major study area is our most accessible mountain range. She established 66 sites in the Santa Catalinas, siting 28 a quarter-mile or more from the Catalina Highway, which winds its way for 30 miles from Tucson's desert floor to the mixed conifer forests atop its highest peaks.

Ten sites are on the slopes of Mount Lemmon and Mount Bigelow and 28 along the Control Road, the rocky road to Oracle on the north side of the mountains.

Each site is 100 meters long and outfitted with 10 pitfall traps - PVC tubes holding large test tubes partly filled with ethylene glycol.

Moore and her students, along with volunteers including Brusca, her husband, deployed the traps for two-week periods in early and late summer in 2011 and 2012.

The field collections are bolstered by the University of Arizona Insect Collection, more than 2 million specimens, representing 22,280 species. At least 2,614 species were found in the Catalinas.

Moore, who is curator of the collection, recently led a project to remodel its home in the Forbes Building, using a $468,000 grant from the National Science Foundation.

The remodeling compacted the specimens into new drawers and cabinets and gave it 50 percent more room to grow.

Moore said the Arizona Sky Island Arthropod Project connects all her responsibilities at UA. "It's local. It combines research, teaching and curation, and it's a good way to get students out into the field."

Moore proposes a 20-to-30-year study of the Catalinas and other Sky Island ranges in Arizona and Mexico that would establish a baseline and document changes in response to climate.

The plant world in which her bugs live has been better studied, and Moore found a convenient corollary to the project's catalog of plant life on the mountain - a 1963 transect of a 20-mile section near the Catalina Highway, done by noted ecologists Robert Whittaker and W.A. Niering.

That comparison found significant movement of plant species, outlined in a paper, "Dramatic response to climate change in the Southwest: Robert Whittaker's 1963 Arizona mountain plant transect revisited." It will be published this month in the journal Ecology and Evolution.

Moore and Brusca's co-authors include climatologist Jonathan Overpeck, and botanists and biologists from the UA, the Arizona-Sonora Desert Museum and Pomona College.

Moore's plots are not exact recreations of Whittaker's, who did not record specific locations and identified plant species only by elevational increments of 1,000 feet.

Because of the uncertainty introduced by Whittaker's 1,000-foot gradients, the paper does not claim movement of plant species unless they are totally outside the range where Whittaker found them.

Even with those conservative estimates, said Brusca, the study found 27 common plant species that had significantly shifted the boundaries of their occurrence upward, apparently in response to warming temperatures and dwindling rainfall.

One of the most amazing and obvious examples, he said, is alligator juniper, which Whittaker found at 3,000 to 4,000 feet in elevation. That elevation is now the domain of grasses and desert scrub. The Moore study recorded the tree's first appearance at 5,000 feet.

Bracken fern, which Whittaker found at the 6,000-to-7,000-foot level, now makes its first appearance at 7,500 feet.

Moore said she, like Whittaker before her, studiously avoided riparian areas, microclimates whose moisture can support plants at lower elevations than normally found. She also avoided areas burned in the Aspen and Bullock fires.

Mean annual temperatures in Tucson have increased at an average of 0.25 of a degree Celsius (0.45 degree Fahrenheit) per decade since 1949, the study notes, with temperatures exceeding the mean in 12 of the last 13 years. Rainfall has been below average in 13 of the last 20 years, reflecting the drought in the Southwest, the paper says.

It's an old story, said Brusca. Plants have been shifting their elevation or latitude ranges in response to climate for thousands of years. "There have been a dozen big climate shifts since the Pleistocene (11,700 years ago). The only thing unusual today is the speed at which it is happening."

The authors say the dramatic shifts recorded in this study, in only 49 years, bolster models that predict upward elevational shifts of mountain plants in response to expected warming of 3 to 6 degrees Celsius by the end of this century.

There is a limit to elevation shifts, Moore said. "In the Catalinas, we have moisture gradients. When climate warms, most species move up. Those at the top are the most vulnerable. They will be pushed off the top or adapt. Either way, it's still stressful for them."

Moore worries that such a thing will happen even before warming takes its final toll.

"Over the long term, it's so depressing, it's fire that's going to decimate our populations more than anything else."

On StarNet: Read more environment-related articles at azstarnet.com/environment

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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