Tillandsia Web, Dade Chapter, Florida Native Plant Society

Online Newsletter

Excerpted from our print newsletter. See the printed newsletter for detailed Field Trip directions and reports, for phone and addresses for yard visits and additional articles. Join now to obtain the benefits of full membership!

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September 2001

In This Issue



Tuesday, September 25, 7:30 p.m. at Fairchild Tropical Garden, 10901 Old Cutler Road.

Stars of the Wildflower World: A Look at the Asteraceae. Speaker: Chuck McCartney.

After the orchid family, there are probably more species of asters, daisies and their kin in the family Asteraceae than any other group of vascular plants, with estimates of 23,000 species worldwide. More than 400 species are reported for Florida, with 130 reported for Miami-Dade County, 57 for the Keys, 43 for mainland Monroe County, and 97 for Broward County. Chuck McCartney, wildflower enthusiast and FNPS member, will share a look at what makes the Aster family distinctive within the plant world and illustrate these traits with color slides, concentrating on the species native to southeastern Florida.

Thanks in advance to refreshment donors Carol Farber (drinks and ice) and Barbara McAdam, Lee and Scott Massey, Jeff Blakley, Gail Romero (snacks). Everyone is invited to add to the refreshment table or bring a native plant for the raffle or auction.

October 23 program. Chris Bergh, Land Conservation Program Manager for The Nature Conservancy's Florida Keys program: "Florida Keys Natural Areas; Acquisition and Management for Biological Diversity". (Chris will lead our November field trip.)

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Field trips are for the study of plants and enjoyment of nature by FNPS members (Dade and Keys) and their invited guests. Collecting is not permitted. Please join today so that you can enjoy all the benefits of membership!

Sunday Sept. 30, Everglades National Park. We will look for flowering members of the aster family (see Sept. meeting) and other early autumn wildflowers along a fire road that runs along the north rim of Long Pine Key, where the pine rocklands meet the rocky glades.

Friday-Sunday, Nov 2-4 (our annual "overnighter") to Lower Keys natural areas (see Oct. meeting). walks will include Blue Heron Hammock in Marathon, rock pinelands and fresh water wetlands on Big Pine Key, and Torchwood Hammock on Little Torch Key. accommodations (also available at upcoming meetings).

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Note: All Dade Chapter members are welcome at all chapter activities. For more information about those planned by the Keys Activities Committee, please call Jim Duquesnel at John Pennekamp Coral Reef State Park, 305-451-1202.

Meeting: Wednesday, Sept. 19, at John Pennekamp Coral Reef State Park. Roger Hammer will present a slide program of some of the 306 plants in his upcoming field guide for wildflowers of the historic Everglades region. Roger is the Park Naturalist at Castellow Hammock Nature Center in Homestead and has worked for Miami-Dade County's Parks and Recreation Department since 1977. There will be the usual native plant raffle and refreshments after the meeting. Anyone donating a raffle plant will receive a free raffle ticket (home-baked cookies earn a hug from Jim).

The park entrance will open (no charge) at 6:45PM and close promptly at 7:30PM, so please arrive on time. A plant identification workshop begins at 7PM (bring a cutting of a mystery plant that includes several leaves and, if possible, fruit or flowers). The meeting begins at 7:30 and the program by 7:45.

Field trip: Saturday, Sept. 22. Crane Point Hammock. Leader: Roland Fisch, Professor at Florida Keys Community College Marathon Campus, teaching Keys ecology and botany since 1976. Crane Point's museum, outdoor exhibits, and trails offer some of the very finest environmental education opportunities in the Keys. The hammock is a wonderful place to learn the native Keys palms and other middle Keys species.

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VOLUNTEERS are needed for our next Everglades National Park Visitors Center landscaping project workday, Saturday, September 15, 9:00 - noon. We will call everyone on the volunteer list. Please call Carrie (305-661-9023) if you plan to attend or if you would like to be added to the master list of volunteers. We will mostly do pruning, weeding, and mulching when we aren’t admiring how nice the project looks after rainfall and a very productive growing season. Please be sure to bring pruning tools, gloves, hand trowels, shovels, wheelbarrows, and your preferred insect repellant. If you can help with calling or bringing refreshments, please call Carrie.

SPECIAL PROGRAM: Butterfly and native plant expert Dr. Marc Minno will present "The Secret Life of Butterflies, Butterfly Love and Life in Your Garden" at 1 p.m. on October 28 at Fairchild Tropical Garden. Marc is a biologist with St. Johns River Water Management District, co-author of four books on butterflies, including Florida Butterfly Gardening, Butterflies of the Florida Keys, and Butterflies Through Binoculars, Florida Edition, and former resident of Broward County. This special program is sponsored by DCFNPS, FTG and others. The program will be followed by book signing (FTG will sell the books) and a butterfly walk at 3 p.m. with Dr. Minno and other butterfly experts. The event is free to the public after admission to the Garden. Members of FNPS (and other sponsoring organizations) and their guests may enter the Garden free to attend this program. FNPS members are asked to RSVP to Lynka Woodbury at 305-667-1651, ext. 3427 (just leave a message).

When science teacher Chris Browlow called the Native Plant Society for help with an empty greenhouse at Lindsey Hopkins Technical Educational Center, member Jim Solly came to her rescue. Imagine a third-floor, downtown greenhouse in Miami without shade cloth, impossibly hot and uninviting. Jim helped make it cool, and now plants and minds are growing nicely there together. Thank you, Jim -- great job! Ms. Browlow is an enthusiastic and devoted teacher, and a visit to her classroom is inspiring. She would welcome other helpers from our group, too. If you are interested, please call Carrie Cleland (305-661-9023).

On June 30, employees from Bank of America and members of Treemendous Miami and DCFNPS participated in a workday at the City of Miami’s Simpson Park, along with park director Pat Quintana and one staff member. Although the Channel Seven news reported "county workers picking up trash", the hard-working volunteers were actually removing exotic trees and vines invading the native hammock of this 8-acre park.

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Tropical Audubon Society. Plant sale Sept. 22 (9am-5pm) and 23 (9am-4pm) featuring native plants common to South Florida and Cuba. Volunteers from DCFNPS are invited to help in sales, check out and support. No experience necessary! Doc Thomas House, 5530 Sunset Dr. 305-666-5111. September 18 meeting: "Native Plants of Cuba and South Florida" at 8pm, social at 7:30. Plant walks led by Rock Cohen (please make reservation at 305-666-5111): Oct.21, Beginning Botany at Matheson Hammock. Nov. 18, Deering Estate at Cutler.

The Miami based non-profit, The Institute for Regional Conservation (IRC), has launched a new web site (www.regionalconservation.org), created by local botanists George D. Gann, Keith A. Bradley, and Steven W. Woodmansee. Among other things, it features The Floristic Inventory of South Florida Database. Users can obtain information on native and naturalized plants of South Florida, and print plant lists for South Florida parks, counties, and habitats. Contact George or Keith at irc@regionalconservation.org or (305) 247-6547.

Miami-Dade Parks Natural Areas Management workdays, 9AM-noon. Call 305-257-0904. 9/15, Coastal Cleanup; 9/22, Boystown Pineland Preserve (SW 112 St. and 138 Ct.); 9/20, Ned Glenn Pineland Preserve (SW 87 Ave. and 188 St); 10/27, Hattie Bauer Hammock (SW 157 Ave and 267 St.). There are also volunteer opportunities in historical research, fund raising and general office work.

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Native Plant Workshop. 3rd Tuesdays at Bill Sadowski Park, 1/2 mile west of Old Cutler Road on SW 176 Street, 7 PM. Call Steve Woodmansee at 305-247-6547 or Roger Hammer at 305-242-7688. The topic for September 18 is the Asteraceae (Sunflower Family).

Fairchild Tropical Garden fall classes include several with "native interest" (and taught by DCFNPS members!): Planting from A to Xeriscape (Jeff Wasielewski, Oct. 17); Xeriscaping with Palms (Chris Migliaccio, Oct. 18); Container Palms (Chris Migliaccio, Oct. 25); Everglades Wildflower Walk (Roger Hammer, Oct. 27); Introduction to Native Plants of South Florida (Gwladys Scott, Oct. 10). Call 305-667-1651 ext. 3322.

If you work in the environmental field, a Certificate in Environmental Studies from FIU could improve your credentials or help you get a promotion. The certificate can be done without formal admission to FIU and involves taking 6 undergraduate or graduate level course, two each in environmental science (+lab), environmental social science and environmental electives. The certificate is appropriate for those who have or are working on a degree. Call the FIU Environmental Studies office at 348-1930.

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by Robert F. Doren

Introduced species have become a significant component of human-caused global environmental change. Even though this fact has been understood for some time, most people, even many scientists have failed to recognize or appreciated the seriousness and potential magnitude of the issue. Biological invaders are capable of altering ecosystem structure and function. The long-term consequences of global ecological alterations in disturbance regimes, nutrient dynamics, soil and water chemistry, changes in species dominance, community composition and structure and recruitment, evapotranspiration, erosion, soil formation, microclimate, competition, etc. are basically unknown.

The wholesale and uncontrolled movement of biological organisms by humans has essentially eliminated the natural biogeographic barriers that originally created and sustained the major floral and faunal regions of earth and are obscuring the distinctiveness of the earth’s biota. While many of these plants and animals are considered essential to human health and welfare and are not regarded as threats to biodiversity, they are often a reflection of other human caused change such as land development, which also threatens biodiversity. Some non-indigenous species have caused enormous economic losses, especially in agriculture. Some species affect the structure and function of ecosystems or the preservation or restoration of native biological diversity. While economic costs may be able to be documented and cost-risk analyses for these species may be possible (although little has actually been done in this regard), the loss of natural ecosystems and native biodiversity is seldom measurable in economic terms and sometimes considered an unfortunate byproduct of economic growth.

Humans affect bioinvasion by eliminating the natural barriers to species movement. Bioinvasion reduces biodiversity through direct loss, extirpation or extinction of species and through introduction of pests and diseases.


Why Do Some Species Seem More Invasive Than Others? Why Do Some Ecosystems Seem More Invasible Than Others? What Contributions Can the Current Science Provide Toward Understanding the Ecology, the Risk, the Prediction, and the Management of Invasion Events?

Recent research has begun to focus on the fundamental questions of invasion ecology, such as "what makes some species more invasive than others?" or "what makes some ecosystems more invasible than others?" While some useful predictive information is becoming available for individual species that are the focus of research projects, useful generalizations applicable to species characteristics overall or ecosystem properties have not developed because sufficient quantitative studies are not currently available.

Several theories have been developed from the available science related to what is generally known about the characteristics of invaders and invaded ecosystems, and the more decided theories developed from specific ecological studies.


Alteration of ecosystem processes theory.

Invasive species that are capable of altering ecosystem processes or characteristics are generally thought to be the most serious of invaders and are likely to have the most dramatic effects on ecosystems. They often differ in life form from native species, and usually cause change either by creating new habitat or modifying existing habitat. Alteration of ecological factors such as hydrology, biogeochemistry, stand structure, resource utilization and competition are well documented in the literature, and the number of invasive species capable of altering ecosystem functions and properties is probably much higher than previously thought.

Disturbance creates gaps theory.

Disturbance is often attributed to enhancement of invasion especially in "island-like" areas such as south Florida in particular where either natural disturbance is prevalent or where significant and widespread human alteration of the natural system has occurred. However there are many examples of exotic species invading undisturbed habitats and out competing native species.

Open-niche theory.

Initially it was thought that if evolution and species migration filled all a plant communities ‘niches’ that community was considered ‘species-saturated’ and was impervious to invasion by exotic species. The scientific evidence related to this concept is inconsistent at best, and more recent research suggests that higher native species richness does not impart resistance to exotic species invasion and some research has even shown a positive correlation of exotic species invasion with high native diversity.

Lack of predators and pathogens theory.

This theory presumes that introduced species become invasive because they are introduced without their natural pests and diseases and with an assumed concomitant reduction in competition. Some species are reported to grow and reproduce more robustly in the absence of predators, indicating that predator-free exotic species may enjoy an advantage over native species, but the lack of predators is not always associated with invasiveness. However, the lack of predators is a key concept in the rationale for biological control.

Faster reproductive potential theory.

Many invasive species show either a rapid vegetative growth rate compared to native homologues. Several species in Florida (such as hydrilla and water hyacinth) are documented to be able to reproduce much faster that the native plants in the same habitat. This theory is closely allied with following concept relating to the questions of poor adaptation in native species versus better adaptation in exotic species.

Poor adaptation in native species theory.

It is unclear whether some native species in their native ecosystem are truly less well adapted or tolerant, or if exotic species are simply better able to utilize existing resources or take advantage of reproductive opportunities (Also see previous theory on faster reproductive potential). Research indicates that the later two concepts certainly apply in many well documented instances, and that invasive species capable of altering ecosystem properties may also create a relatively novel environment to which the native species may no longer be adapted.

Availability increases invasibility theory.

There is convincing evidence that the more available a species is the greater the opportunity for eventual establishment of self-sustaining populations. The increase in availability of new species over time, and the repeated availability of existing species also appears to increase the absolute invasion rate. People are the major cause of species homogenization.


Most if not all of the exotic species that become invasive share many traits that help account for their invasive properties. The theories that endeavor to explain how and why these species are able to become invasive overlap in many instances, and most species share characteristics of invasiveness that includes behavior, genetics, physiology, and demography.

How well do these theories predict species invasiveness or ecosystem invasibility? Unfortunately science currently offers no adequate solutions to this vexing problem. Invasion characteristics of individual species may be predictable using biological characters where sufficient data exist. Broader generalizations are usually limited to plant physiology, species behavior, genetics or demography of single species, or rarely congeneric species.

Invasive species are the second biggest cause of the loss of global biodiversity after habitat loss. Bioinvasion is here to stay and will only get worse if we continue to deal with the problems of exotic species in a piecemeal and parochial fashion. The message is loud and clear–we must act cooperatively, collectively, and decisively–if we are to halt the inevitable loss of our natural environment and other natural resources to non-native invasive species. Business as usual has not and will not work.

Why are invasive exotic plants so widespread and numerous?

Documented introductions of plants into Florida have been occurring for over 200 years, and the numbers of introductions have increased over this period. Over 25,000 exotic species of plants have been introduced into Florida. Accidental introductions have been growing as a consequence of increased commerce and tourism. The more often a species is imported and made more available, the greater chance it will become invasive, and the more different species introduced the greater the chance that one will become invasive.

Why are invasive exotic plants considered undesirable?

Invasive exotic plants cause substantial economic losses, reductions in agricultural production, and significant direct control costs. Billions of dollars are lost each year in the US. Millions of hectares of natural areas are infested with exotic plants with a concomitant loss of native species. Hundreds of rare and endangered species and rare habitats are in jeopardy from them.

How frequently do exotic species establish self-sustaining populations and do they all become invasive?

Approximately 10% of introduced species establish reproducing populations and approximately 10% of those become invasive. However, even a single species may cause severe ecological damage and substantial economic losses. Increased availability of exotic species enhances invasion potential and may accelerate invasion rates. Continued human modification of natural habitats provides additional opportunities for exotic species to become established.

Why do we still introduce exotic plants if some of them can cause so much harm?

Exotic organisms are introduced for economic and social benefit. The ecological and social costs of invasive exotics have been largely ignored and been borne by the general public. Both rates and kinds of introductions have fluctuated widely in response to social, political and technological factors. Commercial trade of living organisms in Florida has grown, increasing the likelihood of additional plants becoming invasive. Plants are not viewed as pests by the current US regulatory and port-interdiction programs.

What’s needed to be able to identify species and predict their potential for invasion?

Scientists are generally able to provide quantitative predictions of invasiveness for individual species where sufficient studies are available. Quantitative predictions of invasiveness for groups of similar plants or congeners, or of ecosystems or plant communities or even regions are more qualitative and therefore less reliable. However, useful systems of prediction and risk-assessment for individual species are being successfully used. A risk-assessment system to evaluate existing and forthcoming species, and a comprehensive invasive species information scheme are needed for Florida and the US.

What’s needed to prioritize and manage "high-risk" species?

Accurate and timely identification of species, comprehensive and user-friendly information are essential for helping identify, locate, prioritize and manage invasive plants. A coherent information system and consistent assessment techniques to determine distribution need to be developed for Florida. A national "Early-Warning" information system is being considered. Objective science-based methods for assessing species risk and evaluating control success need to be developed and employed.

Where are the plants and what’s influencing their distribution?

All regions of Florida and all its ecosystems have populations of naturalized exotics. There are local and regional differences in impacts, in total numbers of species present, and acres infested. South Florida and the Tampa Bay area, have more species and acres of invasive exotic plants than other areas of Florida. Disturbed natural areas, proximity to major points of import, increasing commercial availability of exotics, growing human population and migration, and increasing urbanization probably accounts for the higher numbers of exotics in these two regions.

How many exotic plants are in Florida and how many of them are considered invasive?

1,180 exotic plant species are documented as naturalized in Florida. The Florida Exotic Pest Plant Council has assessed their impacts and invasiveness in natural areas and has identified 125 as serious threats to natural areas. Of those, 65 are considered to be extremely serious and highly disruptive to native plant communities. The report being prepared includes those 65 and giant salvinia as the priority species.

How much do we actually know about exotic species and their distributions?

Generalized distributions, usually from herbarium specimens or routine sightings, are available for the 66 most invasive species and a few others. Detailed distribution maps are available for only four species and only for part of their Florida range, although individual sites, such as parks, may produce local maps of exotic locations as part of a site- or species-focused control program. Generalized distributions can be evaluated using the county sightings surveys (see Figure). Information on the natural history and biology is generally inadequate for the majority of species. The information gap for exotic plants is enormous and hinders both species-focused and ecosystem-level management efforts.

Dr. Robert Doren is a member of the Noxious Exotic Weed Task Team of the Everglades Restoration Program. A later Tillandsia will contain information on obtaining a copy of the team’s final report, which will be available this fall.]

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General information and memberships: 305-255-6404

Contact in the Keys: Jim Duquesnel at John Pennekamp Coral Reef State Park (305-451-1202)

President: Carrie Cleland (305-661-9023)

Vice President: Tony Koop (tkoop@fig.cox.miami.edu)

DCFNPS e-mail: DadeChFNPS@juno.com

DCFNPS Web page: http://www.fnps.org/dade/

Webmaster: Greg Ballinger

FNPS Web Page: http://www.fnps.org/

Tillandsia editors: Patty Phares (305-255-6404 or pphares@mindspring.com) and Jeff Wasielewski

The Dade Chapter Florida Native Plant Society is a 501(c)3 nonprofit organization dedicated to the understanding and preservation of Florida’s native flora and natural areas, and promoting native plants in landscapes.

The chapter includes residents of Miami-Dade County and the Keys. Meetings in Miami-Dade County are on the 4th Tuesday of each month except June, August and December at Fairchild Tropical Garden and are free and open to the public. In June, members and their guests are invited to an evening garden tour on the 4th Tuesday. Meetings in the Keys are held on a varying schedule of dates and locations from Key Largo to Key West. The basic FNPS membership (state and chapter) is $25 per year. Please contact DCFNPS for a membership application.

Please send articles, announcements of local activities and news of interest to the Dade Chapter PO Box or email to the editor (above) by the 15th of each month to be considered for publication the following month.

© 1999-2001 Dade Chapter Florida Native Plant Society, Inc.

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