Current Resiliency

To summarize overall current conditions of PCC population factors and habitat elements, we sorted them into three categories (high, moderate, low) based on the population factors and habitat elements described in Table 3.8 and using methods below. The current condition category is a quantitative estimate based on analysis of the three population factors (inbreeding coefficient, population isolation, and population sampling-relative abundance) and three habitat elements (water quality/availability, herbaceous ground cover, and suitable habitat). Overall population condition rankings and habitat condition rankings were determined by combining the three population factors and three habitat elements. For the population conditions and habitat conditions, we counted each of the condition categories and took the most frequent. For overall conditions, we counted all six of the population factors and habitat elements and took the most frequent. In the case of a tie, we erred on the side of caution and took the lesser of the two categories (e.g., moderate rather than high).

Inbreeding Coefficient

PCC, once connected through core and secondary soils within a 56 sq. mile area, is now separated into 13 populations of varying patches or individual populations that, when combined, total a significantly smaller area than occupied by the historic, interconnected population. A recent genetic analysis of population differentiation and clustering to assess population structure of the PCC also quantified each populations inbreeding coefficient (FIS) numbers (Duncan et al. 2017) (Table 3.6). The differences likely correspond to patterns of fragmentation from urban development and not necessarily from selective pressures maintaining adaptive differences. Little work has been done on the population genetics of wild crayfish populations. We have no comparison for values in crayfish species of expected inbreeding coefficients (Duncan et al. 2017), and treat this as a relative measure. Thus, we ranked individual patches or populations into three numerically distinct breaks: Low when inbreeding coefficients were less than 0.200, moderate when they ranked between 0.200-0.400, and high when results were greater than 0.400 (Table 3.6). For the City of Lynn Haven (LH2 in Table 3.6) and College Point (College Oaks in Table 3.6) where very few PCC were collected after significant attempts at captures, we assumed FIS was lower than 0.200 given their geographic isolation and seemingly almost non-existent population . Three populations ranked in the high category, 8 in the moderate, and 2 in the low (Table 3.8).

Table 3-6 (img)
Table 3.6. Population genetic statistics for each population where more than one individual was sampled: observed heterozygosity (HOBS), expected heterozygosity (HE), and the inbreeding coefficient (FIS).

Population Isolation: A landscape analysis, Least Cost Path (LCP), focused at the patch level, was conducted by Duncan et al. (2017). Resistance layers (r1-r7) representing alternative hypotheses for isolation by resistance based on the input of five species experts are listed in Table 3.7. These layers include the following land-cover types: developed; possibly suitable; undeveloped other soils; undeveloped core soils; undeveloped secondary soils; unsuitable; or urban open land. The resistance values (ranked where a higher number indicates more resistance, or lower likelihood of movement through that land-cover type) used for each resistance layer are shown under the columns for land-cover types.

Table 3.7 (fig)
Table 3.7. Resistance layers (r1-r7) based on expert opinion for how land cover may be influencing least cost paths and genetic connectivity (conditional genetic distance) in Panama City crayfish (Duncan et al. 2017).

There was support for the hypothesis that land cover is affecting genetic connectivity in Panama City crayfish. All models that included land-cover resistance (i.e., least cost and circuit models), with resistance based on expert opinion (Table 3.7) performed better than the null (intercept-only) model and six were ranked higher by model selection (i.e., lower AICc and higher model weight) than the geographic distance model (Duncan et al. 2017). The highest ranked model (lc6) was a least cost path model that showed negative effects of urbanization on genetic connectivity where urban development acts as barriers for crayfish connectivity (i.e., high resistance) and also positive effects of undeveloped core and secondary soils for enhancing connectivity (i.e., low resistance) based on the r6 hypothesis (Duncan et al. 2017) (Figure 3.22 ). We note that there was also support for the simple isolation by distance hypothesis as genetic distance tends to increase with geographic distance in Panama City crayfish. However, this model had weaker support than the highest ranked land-cover layer, and geographic distance was no longer significant when land cover was included in the model. Therefore, this modeling effort suggests that the land cover between populations, as well as the geographic distance, affects the genetic distance between those populations (Duncan et al. 2017).

Least-cost pathways for PCC populations
Figure 3.22. The least cost paths between 9 primary Panama City crayfish populations.

We used the results of the lc6 model to rank population isolation of the PCC populations based on LCP. Populations with a LCP greater than 2 kilometers (km) were ranked low, those between 0.5-2 km were ranked moderate, and those less than 0.5 km were ranked high (Tables 3.7 and 3.8). Similar to our logic for separation distance between sampling points, we used literature on crayfish dispersal distances largely based on migratory and often invasive species. NatureServe recommends a 2 km distance for movement across suitable and unsuitable habitats. The PCC is a small crayfish that does not have large migratory movements, especially through unsuitable habitats, so we erred on the side of caution and used 0.5 km for our minimum separation distance and 2 km for our maximum separation distance. The recent estimates of inbreeding generally support this break but also indicate that other factors may be playing a role in driving inbreeding. For example, Airport-south and Talkington each have a moderate inbreeding coefficient yet have the most connectivity based on shortest LCP. This example indicates that other factors emerge to explain the inbreeding coefficient, such as patch size, which was not included in the LCP models. While these two populations are closest, their combined suitable habitats have a moderate ranking (105 acres, just over the low ranking of suitable habitats). This indicates that use of these two metrics to measure population health is not redundant.

Table 3.8. Population and habitat characteristics within each population used to create condition categories in Table 3.9.
Condition category
Population Factors
Habitat Elements
Inbreeding Coefficient Population Isolation Population Abundance Freshwater Quality & Quantity Herbaceous Ground Cover Suitable Habitat
High >0.400 < 0.5 km >51 <33% developed and unsuitable easements or ROW with >15 acres that is managed >800 acres
Moderate 0.200-0.400 0.5-2.0 km 21-50 33-66% developed and unsuitable easements or ROW with
<15 acres suitable habitat that is managed; or timber lands
100-800 acres
Low < 0.200 > 2 km 1-20 >66% developed and unsuitable no managed lands,
habitat currently a titi monoculture
<100 acres

Population Abundance: Based on survey data from year to year, most populations except those where only a few crayfish were caught had all age (adult, subadult, and juvenile) and sex classes (male and female), so categorizing in this manner was not effective (FWC 2017, unpublished dataset). Those lacking reported age classes were Airport-north, City of Lynn Haven, Industrial, and 231-north. We used the results of these surveys over time to categorize the status of each PCC population based on relative abundance levels. Populations where 1-20 PCC were captured, regardless of age or sex, were considered in the low range; sites where 21-50 PCC were captured were ranked at the moderate range, and sites with greater than 51 PCC’s were put into the high category (see individual population summaries for survey results). Four populations ranked with greater than 51 PCCs captured during a seasonal sampling event ranked high, four ranked moderate with n 21-50 PCC captured, and 5 ranked in the low category (Table 3.9).

Table 3.9. Current resiliency of Panama City crayfish populations. See Table 3.8 for condition descriptions.
Population Name
Inbreeding Coefficient
Population Isolation
Population Abundance
PopulationCurrent Conditions
Freshwater Quality/
& Quantity
Herbaceous Ground Cover
Suitable Habitat
Habitat Current Conditions
Overall Current Condition
Shriners Moderate Low Moderate Moderate Moderate Moderate Low Moderate Moderate
Airport-north Moderate Low Low Low Moderate Moderate Low Moderate Low
Airport-south Moderate Moderate Moderate Moderate Low Moderate Low Low Moderate
Talkington Moderate Moderate Moderate Moderate Moderate Moderate Low Moderate Moderate
City of Lynn Haven Low Low * Low Low High Low Low Low Low
Industrial Moderate Low* Low Low Low Low Low Low Low
St Joe Mitigation Moderate Low High Moderate High High Moderate High High
College Point Low Low* Low Low Low Low Low Low Low
Highpoint Moderate Low Moderate Moderate High Moderate Low Moderate Moderate
Deerpoint High Low High High High High High High High
231-north Moderate Low Low Low High Moderate Moderate Moderate Moderate
Star Avenue High Low High High High High High High High
231-south High Low High High High High High High High

Water Quality and Quantity: We lacked information to categorize sites that may be affected by decreased groundwater levels or polluted ground water. Bay County has a significant population that continues to rely on groundwater for use in homes and business, which alleviates concerns of insufficient ground water quality, yet we recognize that perhaps this withdrawal could impact the species, especially during times of drought.

Surface water quantity and quality are also important habitat features. PCC of all age classes are captured from surface waters, indicting a primary habitat element needed to sustain the species. Surface waters provide shelter for juveniles to grow prior to being large enough to burrow. These locations also provide for breeding and feeding grounds. Water must be sufficiently deep to support the species but shallow enough to sustain herbaceous vegetation.

To quantify possible effects to individual populations, we ranked surface water quality and quantity by adding the percentages of acreage in habitat types labeled developed or unsuitable as compared to the other 5 habitat categories listed in Tables 3.2 and 3.3. This is a proxy measure based on the logic that developed land cover generally indicates a significant level of habitat unsuitable for crayfish, and that these areas contain housing and commercial businesses, where flooding events and standing waters are generally unappreciated and, therefore, removed through storm water control methods. The expedited efforts to move water quickly away likely artificially drains adjacent “natural” habitats. In addition, the “unsuitable” habitat category includes the transportation system (e.g., roads, airports), which are often the source of contaminants such as petroleum products that are likely of concern for invertebrate species such as the PCC.

Populations with habitats quantified as greater than 66% developed and unsuitable were given a low rank for this habitat element. Habitat polygons with 33-66% development and unsuitable habitat were ranked at a moderate score, and anything less than 33% developed and unsuitable was scored at a high rank (Table 3.7). Seven populations ranked in the high category, 3 in the moderate and 3 in the low (Table 3.9).

Herbaceous Ground Cover: Restoration of degraded PCC habitat will result and has resulted in increased cover and diversity of native herbaceous and woody vegetation typical of high-quality wet flatwoods within several conservation easements initially set aside for wetlands mitigation within the PCC’s range. Where prescribed fire is not a management option, mechanical treatment is used to maintain early successional herbaceous groundcover across the irregularly inundated wetland habitats that PCC prefer.

Since 2011, efforts have been made to restore parcels of degraded habitat to make them suitable for PCC. FWC staff has worked closely with FWS staff to identify conservation easements within PCC habitat, establish agreements with landowners, conduct habitat and faunal surveys, implement habitat management, and monitor the progress of such sites in supporting viable PCC populations. We have used the existence of conservation easements within each PCC population as an element of ranking importance because they provide the opportunity to maintain existing pine flatwoods and wet prairie communities or to restore these properties back to an early successional stage. Populations with no easements were ranked low because these habitats are rarely managed and become titi monocultures over time.

With the exception of Shriners, all populations managed on easements less than 15 acres in size were in the low to low-moderate inbreeding coefficient class. We therefore have ranked managed (i.e., mowed or burned) easements or rights-of-way less than or equal to 15 acres in the moderate category for herbaceous ground cover. Land managed in timber was also given a moderate ranking. Post-timber harvest actions in wet flatwoods generally stimulate groundcover until new crops have canopy closure and eventual duff layers that suffocate the groundcover—so boom-or bust situations are given a moderate level, and areas with protected lands with greater than 15 acres of managed habitat such as Gulf Power’s rights-of-way are ranked at a high level. Using this break-out, 4 populations ranked high, 6 were moderate and 3 were low (Table 3.9).

Suitable Habitat: Landscape modeling discussed above supported the expert opinion-based hypotheses that urbanization decreases genetic connectivity in the PCC and that core (primary) and secondary soils predict patterns of increased connectivity, meaning the PCC likely does not move into or through other habitat types that don’t contain these soil types (Duncan et al. 2017). Table 3.2 and Table 3.3 above report the amount of core and secondary soils available within each population polygon. Protected areas must be large enough to support groups that can maintain genetic variability sufficient to prevent inbreeding depression and resist local population fluctuations. Multiple populations increase the likelihood there will always be a source of dispersing individuals to recolonize areas after local extinctions (Soulé and Terborgh 1999, pps 21-22). The three populations with the highest inbreeding coefficient, meaning less inbreeding is occurring, (Star Avenue, 231 south, and Deerpoint) all have at least 800 acres or more of suitable habitats. We therefore used 800 as the minimum acreage needed to get a “high” ranking (Table 3.7). All but two others (231-north and St Joe Mitigation) have lands less than 100 acres. We therefore used this as the cut-off. Lands with less than 100 acres of combined suitable soil types are ranked low, and those 100-800 acres in size as moderate (Table 3.7). Three populations ranked high, 3 ranked moderate, and 8 ranked low (Table 3.9).

Current Resiliency

The overall current conditions were estimated to be high for 4 populations (St. Joe Mitigation, Deerpoint, Star Avenue, and 231-south), moderate for 5 populations (Shriners, Airport-south, Talkington, Highpoint, and 231-north), and low for 4 populations (Airport-north, City of Lynn Haven, Industrial, and College Point) (Table 3.9, Figure 3.6).

Looking at combined Population Factors alone, representing a combination of inbreeding coefficient, population isolation, and population abundance, 3 populations were high (Deerpoint, Star Avenue, and 231-south), 5 populations were moderate (Shriners, Airport-south, Talkington, St Joe Mitigation, and Highpoint), and 5 populations were low (Airport-north, City of Lynn Haven, Industrial, College Point, and 231-north) (Table 3.8).

Looking at combined Habitat Elements alone, representing a combination of freshwater quality & quantity, herbaceous ground cover, and suitable habitat, habitat conditions were high in 4 populations (St. Joe Mitigation, Deerpoint, Star Avenue, and 231-south), moderate in 5 populations (Shriners, Airport-north, Talkington, Highpoint, and 231-north) and low in 4 populations (Airport-south, City of Lynn Haven, Industrial, and College Point) (Table 3.9).