Urban Nature Preserves as Habitats for Rare and Endemic Flora in a Scrubland and Pine Flatwoods Region of the Southeastern United States

Abstract

Florida, USA, has 215 endemic or near-endemic plant species, most of which are found in scrubland and pine flatwood habitats and some of which are globally threatened or endangered. Florida is also one of the most rapidly urbanizing states in the United States, and natural lands are being rapidly replaced by urban development in this state. Conservation easements and nature preserves are two tools for sustaining biodiversity in urbanizing landscapes. This collection of images documents observational research on rare and endemic wildflower species in the nature preserves of Hillsborough County, Florida (population of 1.5 million), part of the larger Tampa metropolitan area (population of 3.2 million). A two-year survey of wildflowers in 27 nature preserves dispersed throughout the county’s total 3.3 km² area observed 410 species across 97 families. Of these 410 species, there were 19 species endemic to Florida, including the critically globally endangered Florida goldenaster (Chrysopsis floridana). Each of these endemic species relies on the unique soil and hydrologic conditions of the Florida scrubland and flatwood ecosystems, and preservation of these lands amidst urban development is critical for their conservation. The objective of this work is to document the role of the nature preserves as habitats for rare and endemic wildflower species, with the goal of providing science-based support for maintaining preserve land within and near urbanizing areas.

1. Introduction

Scrubland and pine flatwood ecosystems have some of the highest species diversity in the southeastern United States and are the dominant natural terrestrial ecosystems in Florida [1]. Both ecosystems are increasingly being disturbed and replaced by human activities and urban development, which threaten their rich biodiversity [2,3].

Nature preserves are land that is set aside and provides protection from surrounding development or alteration. They play important roles in preserving species biodiversity, especially for endemic species that are only found in specific places and nowhere else in the world [4]. Florida has 215 globally endemic plant species, many of which rely on the unique characteristics of the scrubland and pine flatwood ecosystems and are found nowhere else outside of Florida. Like endemic species worldwide, the endemic plant species in Florida have a restricted distribution and small population sizes, which make them vulnerable to anthropogenic threats and extinction [5]. Therefore, nature preserves that maintain the remnants of natural ecosystems are critical to maintaining local endemic species, and setting land aside as a nature preserve is an important in situ conservation strategy for endemic species [6,7].

Nature preserves can also be important for maintaining populations of threatened and endangered species [8], and regularly assessing the efficacy of nature preserves for species conservation is important, especially in highly urbanized areas, where the preserved land may be fragmented or encroached upon by development [9]. Development not only reduces the natural habitat but also fundamentally changes hydrology and resource availability, which may also lead to biodiversity losses [10,11,12,13]. Preserved land and other urban green spaces can be encouraged through ordinances and urban planning [14,15]. The goal of this collection of images is to provide photographic evidence of the role that urban nature preserves can play in providing habitats for endemic and rare wildflower species. This work demonstrates the diversity of species found in a restricted geographic range and can be used to inform policies and urban planning activities aiming to preserve biodiversity in ecosystems facing anthropogenic change.

2. The Study Site

This work presents photographic evidence of wildflower species in Hillsborough County, Florida (27.9904° N, 82.3018° W). All the photographs were taken in nature preserves within Hillsborough County during the years 2020 to 2022. Hillsborough County (with a population of 1.5 million in 2023) is part of the Tampa metropolitan area, which had a total population of 3.2 million people in 2023. This county is rapidly urbanizing and is expected to grow in population by 31% between 2022 and 2050. The county maintains nearly 25,500 hectares of nature preserves, which are dispersed throughout the county’s total area of 3.3 km². The preserves are often surrounded by urban and built-up land uses. The habitat types within the nature preserves include scrubby and pine flatwoods, wet prairies, hardwood swamps, freshwater marshes, open water, and palmetto scrub. Hillsborough County is in a subtropical climate zone, with a distinct wet season from June to September each year. The region receives approximately 140 cm of rain each year, with more than 65% of it occurring during the summer wet season. The area is underlain by limestone geology, with numerous karstic features throughout the county. The landscapes of this area include low plateaus and ridges, flatwoods, prairies, and a variety of coastal features. Its soils are predominantly well-drained sands. During the 2020–2022 study period, 1 of 27 nature preserves within the county was selected one to three times a month and hiked in during the morning hours (07:00 a.m. to 10:00 a.m.) to take photographs of all wildflower species observed. The photographs were cataloged and annotated with the location and date of each observation. Identification of the species in each photograph was verified in the iNaturalist app, which involved uploading each photograph onto the app and obtaining verification of the species identification from at least one other community user such that each identification was graded as “Research Grade” by the iNaturalist user community. iNaturalist is an online social network of community scientists who record their observations of the living organisms in their environments around the world. Observations submitted by users are identified through machine learning tools and community user expertise. To provide added assurance that the species identifications were correct, all the observations were checked against the county conservation management plans, which were drawn up by biological science personnel and include lists of the endemic and rare species found on county lands. These county conservation management plans are available online at https://hcfl.gov/residents/parks-and-leisure/conservation-lands/land-management-plans (accessed 5 September 2024).

After all the photographs were identified to the genus and species levels, endemic and rare species were identified by comparing them to a list maintained by LandScope America, an online collaboration between Nature Serve and the National Geographic Society that serves as a clearinghouse for maps and data about the natural biodiversity across the United States.

3. Images

Over the 2-year study period, 410 wildflower species were observed throughout the Hillsborough County nature preserves (Supplemental Materials Table S1). Of those 410 species, there were 19 species and 1 subspecies endemic to Florida. There were eight rare species that are endangered or threatened. Images of the endemic and rare species observed during the study are presented below, with the endemic species categorized by taxonomic family (

Table 1. Descriptions of endemic species in Figures 1–6.

Figure	Taxonomic Family	Scientific Name	Common Name	Habitat Needs
1A	Asteraceae	Chrysopsis subulate	Scrubland goldenaster	Sandy soils and open ground in pine and oak scrublands
1B		Pityopsis tracyi	Tracy’s silkgrass	Dry, sandy soils
1C		Palafoxia feayi	Feay’s palafox	Dry, sandy soils
1D		Berlandiera subacaulis	Florida greeneyes	Dry, sandy soils
1E		Phoebanthus grandiflorus	Florida false sunflower	Sandy soils of pine flatwoods
2A		Chrysopsis floridana	Florida goldenaster	Florida scrub and sand pine ecosystems; xeric sandy soils with low organic matter
2B		Coreopsis leavenworthii	Leavenworth’s tickseed	Moist, sandy soils of pine flatwoods, from 0 to 20 m above sea level
2C		Lygodesmia aphylla	Rose rush	Dry, sandy soils of pine flatwoods and scrublands
2D		Carphephorus odoratissimus var. subtropicanus	Pineland purple	Hydric to wet–mesic pine flatwoods
3A	Fabaceae	Chapmannia floridana	Florida Alicia	Well-drained sandy soils
3B		Centrosema arenicola	Pineland butterfly pea	Sandy, well-drained and nutrient-poor soils
3C		Dalea adenopoda	Tampa prairie clover	Dry, sandy soils
4A	Lamiaceae	Trichostema gracile	Flatwoods bluecurls	Mesic pine flatwoods and scrubland
4B		Scutellaria arenicola	Florida scrub skullcap	Well-drained sandy soils
5A	Campanulaceae	Lobelia feayana	Bay lobelia	Moist, sandy soils of pine flatwoods
5B	Apocynaceae	Asclepias feayi	Florida milkweed	Mesic pine flatwoods
5C	Commelinaceae	Callisia ornata	Scrub roseling	Nutrient-poor, well-drained soils of the scrublands
6A	Annonaceae	Asimina reticulata	Netted pawpaw	Moist, poorly drained sand of pine flatwoods
6B	Euphorbiaceae	Euphorbia polyphylla	Lesser Florida spurge	Well-drained, low organic matter soils
6C	Cactaceae	Opuntia austrina	Florida prickly pear	Dry, sandy, open areas of pine flatwoods and scrublands

).

3.1. Endemic Species in the Asteraceae Family

A total of 8 of the 19 endemic species are from the Asteraceae family, as shown here and described in Table 1 (Figure 1 and Figure 2). There is also one endemic subspecies from the Asteraceae family shown here (Figure 2D).

3.2. Endemic Species in the Fabaceae Family

There were three endemic species from the Fabaceae family (Figure 3, Table 1).

3.3. Endemic Species in the Lamiaceae Family

There were two endemic species from the Lamiaceae family (Figure 4, Table 1).

3.4. Endemic Species in the Campanulaceae, Commelinaceae, and Apocynaceae Families

There was one endemic species from each of the Campanulaceae, Commelinaceae, and Apocynaceae families (Figure 5, Table 1).

3.5. Endemic Species in the Cactaceae, Euphorbiaceae, and Annonaceae Families

There was one endemic species each from the Cactaceae, Euphorbiaceae, and Annonaceae families (Figure 6, Table 1).

3.6. Endangered Species

Endangered species in the county nature preserves included the Florida goldenaster (Chrysopsis floridana) (Figure 2A and Figure 7) and the giant orchid (Orthochilus ecristatus) (Figure 8). The Florida goldenaster is found exclusively in restricted populations in west–central Florida and depends on maintaining natural fire regimes (with fires every 15–30 years) for germination and seedling establishment [16,17]. It is a short-lived herbaceous perennial with approximately 30 extant populations known to occur [18]. In this study, the Florida goldenaster was found in only 2 of the 27 nature preserves visited (Bell Creek Nature Preserve and Rhodine Scrub Nature Preserve). Attempts have been made to introduce populations of Florida goldenaster into several sites in Hillsborough County, with variable success. Recent work has shown that its occupancy is improved by low soil nutrients and less than 60% litter cover over sandy soils [18].

The giant orchid is not an endemic species in Florida, but like the Florida goldenaster, it is endangered. It is native to Cuba and spread sparsely throughout the southeastern US. Most known occurrences have involved less than 10 plants, and in this study, only one plant each was observed in two nature preserves (Little Manatee River Corridor Nature Preserve and Triple Creek Nature Preserve).

3.7. Other Rare Species

Other rare species, with a status of threatened or near-threatened, included the pine lily (Lilium catesbaei) (Figure 9), Florida milkweed (Asclepias feayi) (Figure 10B and Figure 5B), Florida bluecurls (Trichostema floridanum) (Figure 10A), and bushy aster (Symphyotrichum dumosum) (Figure 10C).

4. Conclusions

This work has presented photographic observations of endemic and rare wildflower species in nature preserves in a highly urbanized area of the southeastern United States. It shows the importance of preserved land and ordinances that protect preserved land in urban areas for biodiversity conservation. It is hoped that this work and others like it can be a resource for policy makers and urban planners to use in advancing protections for the unique habitats that support the species shown here. Future work can expand on this by considering the spatial and temporal patterns in the species distribution and how those may be changing over time in response to urbanization and development.