Posts tagged “rediscovered

A Second Miami Tiger Beetle Population Discovered

Note: This post was largely written in August, however I held off publishing due to the sensitive nature of this discovery. This Friday the U.S. Fish and Wildlife Service proposed listing the Miami tiger beetle as an endangered species and announced the existence of a second population of the MTB. With this official confirmation I’m publishing this post in hopes of contributing some context and further information about this population.

The story of the Miami tiger beetle, Cicindela floridana, a beautifully iridescent tiger beetle presumed extinct but rediscovered in 2007 is unique. This fiercely predatory beetle is a south Florida endemic only known from pine rocklands, a habitat once common in Miami-Dade county but, due to extensive development, today only 1.8% of the metro Miami-Dade rocklands remain.

The entomologist Frank N. Young Jr., an 18 year old student at the time, discovered the Miami tiger beetle from pine rocklands in 1934 at a site in northern Miami-Dade county. However, by 1947 this habitat was lost to development as the native pine rocklands were transformed into the neighborhoods of north Miami and Miami Shores (below).

1947

In 2007, after a 73 year absence and presumed extinction, the Miami tiger beetle was rediscovered near Zoo Miami in pine rocklands. This site is part of the Richmond Heights pine rocklands, the largest contiguous remaining areas of this habitat in metro Miami-Dade. Spurred by this rediscovery entomologists surveyed pine rocklands throughout southern Florida in search of the Miami tiger beetle.

Extensive surveys were conducted in both scrub habitats and most of the pine rockland sites in Miami-Dade, Ft. Lauderdale and Palm Beach Counties (Knisley, 2008). Most were unsuitable probably because they were too densely vegetated or the substrates were mostly oolitic limestone rock with few or no sand patches (Knisley et al. 2014).

Despite these efforts in the years since its remarkable rediscovery the Miami tiger beetle had only been found at a handful of directly adjacent sites in the Richmond Heights pine rocklands. Even the known population is few in number (under a hundred adult beetles observed) and face further threats of vegetation encroachment and potential habitat development (see here for more).

This changed in July when Jimmy Lange, a field botanist at Fairchild Tropical Botanic Garden, and Alyssa Dawson, an intern from Ohio University, were surveying an undisclosed patch of pine rocklands for rare plants (namely Brickellia mosieri, an endangered species) when, as Lange describes it, “[i]n my meanderings I was [documenting] other rare species as I encountered them … when I bumped into a tiger beetle.” But this was not just any tiger beetle, Lange and Dawson found three Miami tiger beetles (Cicindela floridana).

Lange-MTB-2015-3

Lange and Dawson’s discovery offers a small boost to the hopes for the survival of the Miami tiger beetle. But even with the discovery of the second population the MTB is still in danger. The MTB habitat, pine rockland, has been extensively developed and today only 1.8% of the metro Miami-Dade pine rocklands remain. These habitats are also under the constant threat of vegetation encroachment primarily due to the lack of controlled burns (which pine rocklands depend upon).

A major question regarding this second population of MTBs is whether the discovery of new populations would alter the expert’s rating of the species as seriously imperiled and  recommendation for formal protections (Knisley et al. 2014). In brief this second population does not significantly alter the Miami tiger beetle’s current standing. First, this “population” is represented by three observed beetles and thus likely does not provide a sufficient number of individuals to contribute to the species survival. Second, Knisley et al. (2014) account for the existence of other populations in their recommendation methods:

Examples of our grading system are as follows: A 1 would be comparable to the NatureServe grade of 1, usually with five or fewer known populations and significant threats; a 1+ would be at the upper range of these factors and 1- at the lower range.

For the 1 +/- grade given by Knisley a species must face significant threats which is absolutely the case for the MTB. Most significantly both populations face the “loss, degradation, and fragmentation” (USFWS) of habitat, primarily from the constant encroachment of vegetation, both ecological succession due the lack of fires and invasive species.

Of particular note the U.S. Fish and Wildlife Service did not release the location of this new population due to the threat of collection:

Tiger beetles are in high demand and avidly collected. We are aware of internet advertisements for the sale and trade of other florida tiger beetles.

Lange-MTB-2015-2


Presumed extinct, Floridian tiger beetle rediscovered after 73 years

It is about five in the morning on a warm August day and I am sitting in the Richmond International airport. I am waiting to board a flight to Miami, Florida where I will be meeting up with Dr. Barry Knisley, researcher and authority on tiger beetles.

Florida is home to many species of tiger beetles including several endemic to the state. However, the habitats of a number of species are today threatened by urbanization or the development of land for agricultural use, particularly for Florida’s ubiquitous citrus crops. One of these endemic tiger beetles is the strikingly green-colored  floridana form of the minute species Cicindela scabrosa.

This form was first collected in August of 1934 by Frank N. Young and formally described five years later by O.L. Cartwright as a subspecies of Cicindela abdominalis. Cartwright’s description was composed of two brief sentences in the June 1939 Annals of the Entomological Society of America:

Differs from abdominalis in the shinning green color of head, thorax and elytra, the later with purplish reflections posteriorly at the sides, and in the strong deep punctures and fovea of the elytra. The green color will also separate this variety from the variety scabrosa Schaupp.

Additionally, Cartwright notes that Young collected 21 specimens which were divided between museums and private collections:

Holotype and 20 paratypes collected at Miami, Florida, August 9-12, 1934, by Frank Young. Holotype deposited in the U.S. National Museum, paratypes in the collections of California Academy of Science, Museum of Comparative Zoology at Harvard, and in the private collections of F. N. Young, W. M. Gordon, M. A. Cazier, J. W. Angell and the author.

One of the USNM paratypes

Cicindela scabrosa var floridana is a member of a complex of closely related, small cicindelids. The archetypal species in this complex, which also includes C. highlandensis, is Cicindela abdominalis. There has long been much confusion over the relation between these species; at one point there were no less than three synonymous species names for both Cicindela abdominalis and C. scabrosa. In his 1984 treatment of the Cicindela abdominalis complex, Choate elevated Cicindela scabrosa to a full species and placed Cicindela abdominalis floridana as a synonymy of Cicindela scabrosa, attributing the green color to be a sign of recent emergence.

Years after his discovery of C. scabrosa var floridana, in communication with fellow entomologists, Young reported that he collected the specimens in the area surrounding Barry College. Unfortunately, this area, like so much of the neighboring region, had been heavily developed in the intervening time. Several researchers, including Knisley, surveyed numerous Miami-Dade county parks and area preserves for C. scabrosa var floridana but without success.

Approximate view of the original collection site(s) in 1999. Image courtesy of the U.S. Geological Survey

In their 2006 field guide to the tiger beetles of North America, Pearson, Knisley, and Kazilek noted:

An isolated population [of C. scabrosa] in the Miami area has been considered as a subspecies, C. scabrosa floridana Cartwright, which is smaller … and distinctly green above. This population … may now be extinct, probably because of habitat destruction and urbanization.

And so with no suitable habitat remaining and no beetles seen since 1934, despite extensive surveys, this form was presumed to be extinct.

But in September of 2007, over 70 years after this species had last been observed in the wild, a population of Cicindela scabrosa var floridana was rediscovered on privately-owned land in the greater Miami area. Jeff Slotten, a lepidopterist, happened across this population while surveying for butterflies and, being familiar with this species, was well aware of the significance of his discovery. He contacted Barry and a fellow tiger beetle enthusiast, David Brzoska; they set about surveying potential habitats and soon found another population at a directly adjacent site.

The area upon which much of present-day Miami sits was once covered by pine rocklands. This fire-dependent community, found on limestone outcroppings, is comprised of a sparse canopy dominated by Florida slash pine, Pinus elliotti var. densa, and a varied understory which includes many endemic plant species. This habitat once stretched from the Florida Keys up to the northern edge of Miami-Dade County, but in the 1940’s the invention and ensuing widespread use of the rock plow marked the destruction of the majority of Floridian pine rockland.

Today, only a fraction of the original Miami pine rockland habitat remains; by some estimates as little as 2%. Moreover, most of these remaining areas are quite small and often widely separated by miles of heavy development. In addition, many of these remaining pine rocklands now face a new danger; due to the lack of fire, they are being overrun by both native and non-native vegetation as the habitats are transitioning to hardwood hammocks.

Shortly after my arrival in Miami, Barry and I are on the road, heading to survey a potential habitat. Unfortunately the most promising area, within a neighborhood park, was an overgrown mess of vines and small hardwood trees. This turns out to be the norm; while we visit several potential habitats, they too are all overgrown. It was evident that vegetation had been growing unchecked for years and no attempt at maintaining these habitats had been made.

We next head to the site where C. scabrosa var floridana was first rediscovered. This area, along with several other parcels of land, is bordered on one side by a highway while a large development wraps around the other sides. Despite this encroachment there remains a sizable area of pine rockland which, thanks to controlled burns, is in exceptional condition.

An open patch of sand, ideal habitat for C. scabrosa var floridana; notice the charred remnants of a tree on the ground.

Barry and I weave through the clumps of saw palmetto toward a sandy exposure and we pause at the edge. Before long there is a hint of movement and a small tiger beetle darts from the base of a blade of grass towards the center of the sandy patch.

There’s a beetle here…

Its coloration is unique; it is dark, not black, but rather a deep iridescent bronzy-green hue. We inspect several other patches and see a fair number of beetles; the temperature is over 90 degrees and the beetles are very active. Most are moving in and out of the sparse patches of shade or sporadically about the sandy areas, occasionally darting after an ant.

Barry watches a patch of habitat for floridana

Trying to photograph one is particularly difficult; not only are the beetles fast and small, but there are also jagged chunks of limestone sticking out of the sandy ground making it difficult to move about. On my hands and knees, I slowly approach a beetle but it flies off. Again I approach a beetle; it also takes flight. At last I come across a more cooperative beetle and manage a couple quick shots before it also darts away.

A male C. scabrosa var floridana

A weathered chunk of limestone sticks out of the sand

The next day Barry and I set out to survey another promising site; this one borders the area where C. scabrosa var floridana was rediscovered. We do notice some suitable habitat, but most of the ground is covered with a layer of pine needles from the dense canopy. For over an hour there is no trace of the beetles; at last we find a more open area near the edge of the trees.As we walk through the low vegetation, first Barry and then I see a flash of movement, as if a tiger beetle were taking flight. However, neither of us get a good look and only when we spot a stationary beetle are we sure of what we saw. After this exciting find we drive to the second site where floridana was rediscovered. This property sits next to the first site and has also been maintained by controlled burning.

But, on the portion of this property bordering the development, there is a considerable amount of encroaching vegetation which threatens to choke out any exposed sandy areas. The last time it was burned was clearly several years prior to our survey and, as one might suspect, we found no beetles in this area. Moving on, Barry and I find a larger patch of habitat and soon catch sight of more beetles. Here the ground is quite rocky and the saw palmettos are tightly packed, so I am unable to get a decent chance to photograph the beetles in their habitat. I settle instead for a few shots of some beetles which Barry nets as we continue the survey.

Slowly moving in towards a beetle

Barry carefully holds a female during the survey

This form is small, with a body length under 1cm.

As it comes closer to mid-afternoon we wrap up the survey and I begin to prepare for my return; though very short, this trip has been particularly productive. My flight leaves Miami International as the sun sets, my goal reached – I have the pictures I hoped for.

Over the past couple of years, Barry has worked along with Brzoska and Slotten in examining several differences between this form and the closely related members of the C. abdominalis complex. Based on morphological, seasonal, and distributional differences, C. scabrosa var floridana has been elevated to a full species, Cicindela floridana, in a soon to be published paper.

A side-by-side comparison of the four species of the C. abdominalis complex (L-R): C. floridana, C. scabrosa, C. abdominalis, C. highlandensis.

A captive C. floridana showing the vivid green color, reduced maculations, and bright red abdomen.

While the populations appear to be stable, this species requires more research and management; particularly, the remaining habitats must be sufficiently maintained. Controlled burns should be regularly conducted, as they are the first and most critical steps toward control of the encroaching vegetation. With proper care and protection this species, can come to thrive again.

Acknowledgments:

Special thanks to Barry Knisley for facilitating my trip to Florida and providing the specimens for the captive and comparative photograph. Also thanks to Art Evans for assistance in accessing the USNM collection.

References:

Cartwright, O.L. 1939. Eleven new American Coleoptera (Scarabidae, Cicindelidae). Annals of the Entomological Society of America 32:353-364.

Choate, P.M. 1984. A new species of Cicindela Linnaeus (Coleoptera: Cicindelidae) from Florida, and elevation of C. abdominalis scabrosa Schaupp to species level. Entomological News 95: 73-82.

Pearson, D.L., Knisley, C.B., Kazilek, C.J. 2006. A field guide to the tiger beetles of the United States and Canada. Oxford University Press, New York 8 + 227pp.

U.S. Fish and Wildlife Service. Multi-Species Recovery Plan for South Florida: Pine Rocklands. www.fws.gov/southeast/vbpdfs/commun/pr.pdf