Microhabitat and time-since-fire: effects on demography oF Eryngium cuneifolium (Apiaceae), a Florida scrub endemic plant

Eryngium cuneifolium Small. (Apiaceae) is a narrowly distributed endemic found only in Ceratiola ericoides (Florida rosemary)-dominated Florida scrub, a periodically burned, shrub-dominated habitat. Multivariate analyses using 22 ∗∗∗microhabitat characteristics indicated significant microhabitat and time-since-fire effects on survival, growth, and fecundity of 1287 individuals over a 4-yr period. Survival increased with distance to the nearest shrub, and plants in larger open patches had greater survival rates. Neighboring shrubs of Ceratiola ericoides and Calamintha ashei were associated with a higher mortality of E. cuneifolium than other neighboring shrub species. Survival was reduced by two-thirds over 4 yr (14% vs. 42%) for E. cuneifolium near C. ericoides. Sand accretion increased growth and fecundity. With greater time since fire, woody shrubs increasingly dominate and open patches shrink, significantly reducing survival, growth, and fecundity of E. cuneifolium. Effects were particularly dramatic between 2 and 7 yr postfire, when annual mortality increased from <10% to >30% (r = 0.74). This herbaceous species is dependent on an open habitat maintained by periodic fire. Belowground competition or allelopathy from shrubs probably restricts E. cuneifolium to recently burned, open patches within the most xeric parts of Florida scrub.     

Allelopathic effects of <Emphasis Type="Italic">Ceratiola ericoides</Emphasis> (Empetraceae) on germination and survival of six Florida scrub species

Allelopathic inhibition of germination by Florida scrub plants has been demonstrated in the greenhouse and lab, but not in the field. We studied the allelopathic effects of Florida rosemary (Ceratiola ericoides) roots, leaves, and litter leachates on field germination and three-month survival of six Florida scrub species, three habitat generalists (Lechea deckertii, Palafoxia feayi, and Polygonella robusta), and three rosemary scrub specialists (Hypericum cumulicola, Lechea cernua, and Polygonella basiramia). We used AIC and model averaging to evaluate support for a series of non-exclusive hypotheses. Species varied in germination (2.7–24.6%) and survival (39.2–71%) percentages, and in their sensitivity to leachates. Germination of scrub species was most negatively affected by leaf > root > litter leachates, although not all species followed the overall trend. Additional germination suppression by leachate combinations (relative to single leachates) was minimal. Sites did not vary in germination, but seedling survival did differ among sites. This study further documents the negative impact of Florida rosemary leachates on the germination of co-occurring plant species. Allelopathy may be partly responsible for bare sand gaps in Florida rosemary scrub, and therefore be one of the forces structuring Florida rosemary scrub ecosystems.     

Competitive abilities of three narrowly endemic plant species in experimental neighborhoods along a fire gradient

We conducted field experiments manipulating lichens, shrubs, and herbs along a time-since-fire gradient and assessing effects on three endemic herbaceous species of Florida scrub: Eryngium cuneifolium, Hypericum cumulicola, and Polygonella basiramia. Responses included seed germination, survival, biomass, and fecundity. Transplants into recently burned patches generally had higher survival, larger biomass, and greater reproductive output than transplants into long-unburned patches. Open areas and sites near oaks frequently were more favorable than sites near Florida rosemary. Ground lichens did not affect germination but increased mortality rate of seedlings. Neighboring small shrubby and herbaceous species did not affect the performance of these species. Of the three species, naturally occurring E. cuneifolium were farthest from large shrubs, and their microhabitats had the least ground lichens and shrubs. Eryngium cuneifolium and H. cumulicola are capable of forming persistent seed banks and their recruitment after fire depends mostly on these dormant seeds. Polygonella basiramia relies on seed dispersal and immediate seed germination to colonize recently burned patches. Management for these species should involve variable fire regimes to allow all three species to persist along with many other scrub endemics.     

Gap ecology in Florida scrub: Species occurrence,diversity and gap properties

Questions: Studies of gap effects have been conducted mainly in forests. We studied gap ecology in a pyrogenic Ceratiola ericoides (Florida rosemary) dominated shrubland and asked: How do gap size and the frequency of large gaps change across the fire chronosequence? Do larger gaps differ from smaller gaps in vegetation structure or species diversity? Are effects of gaps independent of, or dependent upon, time‐since‐fire? Are larger gaps refugia for herbs and subshrubs? Location: Archbold Biological Station, Lake Wales Ridge, south‐central Florida, USA. Methods: We investigated plant species occurrence and diversity in 805 gaps (areas free of shrubs taller than 50 cm) in 28 fire‐dependent Florida rosemary scrub sites. We collected quantitative cover data in a subset of seven sites. Results: Gap area distribution was lognormal. The largest gaps occurred throughout all but the longest time‐since‐fire intervals. Gaps were smallest in the longest unburned site but otherwise did not show strong patterns across the fire chronosequence. Species diversity measures increased with increasing gap area, with herbaceous diversity increasing with both gap area and bare sand. Herb diversity (H') decreased with time‐since‐fire. Larger gaps are refugia for some species. Of 14 species occurring in 25–75% of gaps, 13 had increased occupancy with increasing gap area, and gap area was the strongest predictor of occupancy for seven species of herbs and shrubs. Time‐since‐fire was the strongest predictor of occupancy for five species, including four ground lichens that increased with time‐since‐fire. Conclusions: Community structure within Florida scrub gaps is influenced by gap size, which in turn is affected by fire, the dominant ecological disturbance. We present a conceptual model that considers both gap size and time‐since‐fire as drivers of community structure and herbaceous plant diversity in Florida scrub. Because gap properties (independently of fire) have strong influences on species assemblages in Florida rosemary scrub gaps, fire management should consider the number and size of gaps across the landscape.     

Effects of biological soil crusts on seed germination of four endangered herbs in a xeric Florida shrubland during drought

Soil crusts of rosemary scrubs in south-central Florida were examined for effects on seed germination of four herbs that are killed by fire and must recruit from seed: Eryngium cuneifolium (Apiaceae), Hypericum cumulicola (Hypericaceae), Polygonella basiramia (Polygonaceae), and Paronychia chartacea ssp. chartacea (Caryophyllaceae). Biological soil crusts in these sites are dominated by algae, cyanobacteria, fungi, and bacteria. Because crusts can change soil stability, water, and nutrients, they can affect seed germination. A series of greenhouse and field experiments were designed to first examine the effects of crusts in isolation and then to determine their role in the context of other environmental factors – time since fire and distance to the dominant shrub in this system, Ceratiola ericoides. In the greenhouse experiment, germination in autoclaved crusts was dramatically reduced relative to germination in living crusts for all but P. basiramia. In four field experiments where crusts were left intact, disturbed (mechanically or by flaming), or completely removed, the effects of crusts were variable and species-specific, but were significant enough to impact aboveground population sizes. More germination was consistently observed in recently burned sites away from C. ericoides shrubs. Overall rates of germination were generally very low during this study, possibly as a result of seasonal droughts that could have reduced germination, increased seed dormancy, and/or decreased seed viability. The importance of water for germination was confirmed in an experiment with two watering regimes and three crust treatments designed to create a gradient of soil water availability. Germination was significantly greater in the high water treatment and unaffected by soil crust moisture. Dry years are not uncommon in scrub and the results of this study help us to understand how scrub herbs fare during drought and what role biological soil crusts play in germination.     

Hypericum cumulicola demography in unoccupied and occupied Florida scrub patches with different time‐since‐fire

1 Metapopulation models predict that unoccupied, but suitable, patches will exist for species subject to extinction and colonization dynamics. We compared the demographic responses of Hypericum cumulicola , a rare herbaceous species almost entirely restricted to Florida rosemary scrub, when transplanted to occupied or unoccupied patches.
2 Seedlings were transplanted and seeds buried into Florida rosemary scrub patches differing in time since last fire, and in the presence or absence of H. cumulicola. We used a replicated, factorial design to place the transplants and seeds in the field, and monitored their performance for 18 months.
3 Neither time‐since‐fire nor prior H. cumulicola site occupancy affected survival of transplants. Only time‐since‐fire affected growth. Time‐since‐fire, H. cumulicola occupancy, and their interaction affected reproductive effort, but these effects were not consistent between years.
4 Flowering and seed production led to subsequent seedling recruitment near transplants, mainly in recently burned sites. Genetic screening of transplants and seedlings showed that transplants in occupied sites could have crossed with nearby resident plants, but that offspring in sites previously unoccupied were likely to have been parented only by nearby transplants.
5 Seeds buried, and later exhumed, germinated after 1 or 2 years of burial, demonstrating a persistent soil seed bank from which populations could recover after fire. Neither time‐since‐fire nor H. cumulicola occupancy affected seed dormancy or germination.
6 Similar demography in unoccupied and occupied patches suggests that the patchy pattern of site occupancy by H. cumulicola is probably due to limited dispersal and periodic extinction, especially associated with long fire‐free intervals. Conservation measures need to protect unoccupied patches to allow metapopulation dynamics and persistence.     

Damage of alpine vegetation by the 2009 fire on Mt. Shirouma, central Japan: comparison between herbaceous vegetation and Pinus pumila scrub

A fire occurred (0.59 ha) in an alpine fellfield (2600 m a.s.l.) on Mount Shirouma, central Japan, on 9 May 2009 before the start of the growing season. Herbaceous plants and dwarf pine Pinus pumila dominated the site. Plots were established in burned and unburned herb vegetation and P. pumila scrub just after the fire to monitor vegetation recovery. This study reports the short-term monitoring results 3 months after the fire. Burned herb vegetation mostly recovered by late August 2009. However, burned P. pumila did not recover, and other alpine plants were scarce in burned P. pumila scrub. The observed number of species in herb vegetation was 15–20 m⁻² whereas it was only 1–6 m⁻² in P. pumila scrub. The total cover of plants was 111–129% for burned herb vegetation but was only 8–31% for burned P. pumila scrub. Although the species composition in P. pumila scrub distinctly differed between burned and unburned plots, in herb vegetation it was similar between them. Therefore, P. pumila scrub was greatly damaged by the fire, whereas herb vegetation was not damaged. Rapid recovery of herbaceous plants was because winter buds in the soil were not damaged by the fire, but winter buds on shoots of P. pumila were burned. Therefore, the difference in winter bud location (above or belowground) may have resulted in the difference in damage between herbaceous plants and P. pumila.     

Population structure and spatial pattern in the dioecious shrub Ceratiola ericoides

Abstract. The dioecious shrub Ceratiola ericoides (Florida rosemary) dominates xeric, infrequently burned Florida scrub vegetation, often to the near-exclusion of other woody species. We studied the spatial pattern, age, sex and size structure of four populations in Florida, USA: two coastal scrub populations subject to recurrent local disturbances due to sand movement, and two inland scrub populations in sites periodically burned by stand-replacing fires. The age structure of individual genets was estimated from node counts and used to describe the age structure of the populations. The sex ratio of males to females was not significantly different from 1:1, except within a female-biased coastal population subject to frequent sand movement. Node counts indicated that the mean age for reproductive individuals was 15 - 16 yr for the inland populations and 13 - 16 yr for the coastal populations. In all sites, there was no difference in mean age between males and females. Vegetative reproduction was uncommon except for the least-disturbed coastal population where 72 % of the reproductive individuals originated through layering. Individuals were generally randomly dispersed at the coastal sites, whereas significant aggregation of males and females occurred in the inland sites where the populations were initiated following fire. Seedling recruitment was continuous in the disturbed coastal scrub site, where 35% of the individuals were juveniles. Most juveniles were dispersed from 0.5 to 0.75 m around females. At one of the inland sites, where juveniles comprised 11% of the population, juveniles were clustered at 0.25 to 5.75 m around females. Coastal populations were all-aged, while inland populations were uneven-aged. Recruitment appears to follow periods of disturbance; infrequent fire in the inland populations and continuous sand movement on the coast are factors initiating recruitment.     

Ecological metrics predict connectivity better than geographic distance

We use microsatellite loci to examine genetic structure of the Florida scrub lizard (Sceloporus woodi) and test for the effects of landscape variables at the scale of neighboring patches. We evaluate ecological metrics of connectivity with genetics data, which to our knowledge is the first application of these particular metrics to landscape-level genetics studies in Florida scrub. Florida scrub is a highly threatened ecosystem in which habitat patches are remnants of a previously widespread xeric landscape. Analysis of mitochondrial DNA (mtDNA) has shown that landscape structure influenced the evolutionary history of the Florida scrub lizard (S. woodi) across its range. Our results concur with these mtDNA studies in documenting divergence between xeric ridge systems and also demonstrate divergence at very local scales. Both least-cost distance and pairwise isolation (a metric used in ecological studies that includes patch size, quality and a modified isolation index) were better predictors of genetic distance than Euclidean distance, indicating that mesic and hydric habitat influence spatial patterns in genetic variation. Our results support the need for focusing on spatial distribution of scrub habitat at the scale of neighboring patches, as well as regionally, in conservation management and restoration. Also, our study points to the value of integrating landscape ecology metrics into landscape genetics.     

Allelopathic effects and root distribution of Ceratiola ericoides (Empetraceae) on seven rosemary scrub species

We studied the root distribution and the effects of leachates from the dominant shrub in rosemary scrub, Florida rosemary (Ceratiola ericoides), on germination of seven subordinate rosemary scrub species. For rosemary scrub specialists, (Eryngium cuneifolium and Hypericum cumulicola), germination was suppressed by the leaf and litter leachates. For species that are not found exclusively in rosemary scrub (Liatris ohlingerae, Polygonella basiramia, Paronychia chartacea, and Palofoxia feayi) litter and leaf leachate did not suppress germination significantly. Species limited to gaps in rosemary scrub (E. cuneifolium, H. cumulicola, and Lechea deckertii) showed reduced germination from rosemary leachates while species not limited to rosemary-free gaps (L. ohlingerae and P. feayi) were not affected by rosemary leachates. Rosemary root abundance was greatest near shrubs, at a shallow depth, and at sites not recently burned. As rosemary scrub patches age, rosemary roots are more likely to interact with herbaceous species in gaps.     

Demographic responses of Pinguicula ionantha to prescribed fire: a regression-design LTRE approach

This study describes the use of periodic matrix analysis and regression-design life table response experiments (LTRE) to investigate the effects of prescribed fire on demographic responses of Pinguicula ionantha, a federally listed plant endemic to the herb bog/savanna community in north Florida. Multi-state mark–recapture models with dead recoveries were used to estimate survival and transition probabilities for over 2,300 individuals in 12 populations of P. ionantha. These estimates were applied to parameterize matrix models used in further analyses. P. ionantha demographics were found to be strongly dependent on prescribed fire events. Periodic matrix models were used to evaluate season of burn (either growing or dormant season) for fire return intervals ranging from 1 to 20 years. Annual growing and biannual dormant season fires maximized population growth rates for this species. A regression design LTRE was used to evaluate the effect of number of days since last fire on population growth. Maximum population growth rates calculated using standard asymptotic analysis were realized shortly following a burn event (<2 years), and a regression design LTRE showed that short-term fire-mediated changes in vital rates translated into observed increases in population growth. The LTRE identified fecundity and individual growth as contributing most to increases in post-fire population growth. Our analyses found that the current four-year prescribed fire return intervals used at the study sites can be significantly shortened to increase the population growth rates of this rare species. Understanding the role of fire frequency and season in creating and maintaining appropriate habitat for this species may aid in the conservation of this and other rare herb bog/savanna inhabitants. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of Hurricanes on Rare Plant Demography in Fire‐Controlled Ecosystems

Hurricanes have dramatic effects on forest vegetation, but their effects on shrublands have rarely been studied. We analyzed the effects of three 2004 hurricanes—among the strongest on record in Florida—on vital rates of 12 rare plant species of pyrogenic interior Florida scrub and sandhill. Tree damage varied by vegetation type (being highest in areas with Pinus clausa) and was associated with debris deposition. Most rare species were minimally impacted by hurricanes. The two most frequently damaged species were the shrubs Prunus geniculata (11% of individuals) and Asimina obovata (7%); both were resilient to damage. Prunus geniculata had little mortality during the hurricane year but damaged plants had a temporary (1‐yr) reduction in relative growth rate. Prunus geniculata flowering was unaffected by hurricane damage. Hurricane damage had no effects on vital rates of A. obovata, Eriogonum longifolium var. gnaphalifolium, or Chrysopsis highlandsensis. Other species suffered little or no observable hurricane damage. Of 12 species analyzed, nine had similar annual survival in hurricane and nonhurricane years. Relatively low survival in the hurricane year (compared with other years) was linked to prehurricane drought or prescribed fire in two of three species. Thus, the 2004 hurricanes did not have important effects on populations of interior Florida scrub and sandhill plants, especially herbaceous species. This is in marked contrast to dramatic demographic responses to fire in central Florida and strong effects of hurricanes in coastal Florida, highlighting that these different disturbances may have divergent effects on vegetation and populations over short distances.     

Microhabitat distribution of two Florida scrub endemic plants in comparison to their habitat-generalist congeners

Habitat-specialist species may be restricted to a narrower range of microhabitats than habitat-generalist species. We addressed this hypothesis by comparing microhabitats of two pairs of congeners that differ in habitat specificity and co-occur in one distinct habitat type, Florida rosemary scrub. We characterized microhabitats of rosemary scrub specialists, Polygonella basiramia and Lechea cernua, their habitat-generalist congeners, Polygonella robusta and Lechea deckertii, and random points in the rosemary scrub habitat. Plants of both habitat specialists occurred in microhabitats with significantly more bare sand than plants of habitat-generalist species and random points. Plants of all four species occurred in microhabitats that were farther from dominant shrubs, Ceratiola and Quercus spp., than random points. Seedlings of both habitat specialists grew larger in bare sand microhabitats, whereas ground lichens and litter did not affect seedling growth of the habitat generalists. As the time since fire increases, bare sand cover decreases, Ceratiola density increases, Quercus density remains constant, and shrubs become taller. Physical characteristics, such as soil temperature, soil carbon, and soil moisture, differ slightly with respect to microhabitat. Our results suggest that P. basiramia and L. cernua are specialized on bare sand microhabitats that characterize their preferred habitat, rosemary scrub. Microhabitat specialization may limit the distribution of these rare species.     

Population dynamics of Japanese serow in relation to social organization and habitat conditions. II. Effects of clear-cutting and planted tree growth on Japanese serow populations

Population responses of Japanese serow (Capricornis crispus) to clear-cut logging and planted tree growth were studied by a direct count of the number observed in three areas, Takiyama (305 ha), Gentouziro (270 ha), and Tanokashira (324 ha), near Wakinosawa Village, Aomori Prefecture, Japan, during 1976–89. At Takiyama, a mature mixed forest ofThujopsis dolabrata var.hondai andFagus crenata decreased from 73 to 39% coverage of the area due to clear-cutting during 1978–83. The serow population maintained a relatively low stable density (3–6 individuals per km²) until 1985–87, and increased 5–10 years after the clear-cutting, reaching 9–10 km⁻² in 1988. At Gentouziro and Tanokashira, young plantations of Japanese cedar (Cryptomeria japonica) covered about half of each area. The population densities between 1980 and 1983 were relatively high (14–19 km⁻²), but declined thereafter, reaching 10–14 km⁻² in 1988–89. These results indicated that the density increase resulted from an improvement of food supply due to growth of scrub following the clear-cutting, and that the density decline resulted from a habitat change due to growth of planted Japanese cedar and a decrease in the food supply. In Wakinosawa Village, serow density began to increase 5–10 years after forest cutting, and the high population density, about three- or six-fold larger than that in mature forest, is expected to be maintained for about 20 years after logging.     

Community structure and demography of small-mammal populations in insular montane forests in southern India

bstract Small mammals were studied in insular montane forest patches in the Upper Nilgiris in southern India from February 1994 to September 1996. Nine patches were selected at two sites, one with a single large 600-ha patch, the other with several small patches ranging in size from 0.2 to 60 ha. The population characteristics and community structure of small mammals were studied in relation to patch size and habitat structure within the patches. The two most abundant species were Rattus rattus (2–36 individuals/ha) and Suncus montanus (0–11 individuals/ha), while the abundance of seven other species recorded were very low. The population characteristics of R. rattus examined were density, biomass, proportions of juveniles, sub-adults and adults, mean weight of all animals, mean weight of adults, sex ratio and persistence. The proportion of adults, sub-adults, mean weight of animals, and mean weight of adult males were correlated with patch size. Persistence of sub-adult females in the large patch was especially high. The density and biomass of other small-mammal species were also studied. Two indices of diversity, species richness and proportion of R.␣rattus were compared as measures of community structure. Seven habitat characteristics were measured; of these, canopy cover, canopy height and tree density were correlated with the size of the patch. Density and biomass of species other than R. rattus and proportion of R. rattus were correlated with canopy height. Density and biomass of species other than R. rattus were highest in smaller patches. While the population characteristics of R. rattus may be affected by patch size, the density of rare species may be influenced by factors related to lower canopy height. Migration between patches may be an important factor in maintaining populations in these patches. Received: 5 January 1998 / Accepted: 23 March 1998     

Restoration of Florida scrub vegetation in an old field through 23 years after planting

Florida scrub, a fire‐maintained, xeromorphic shrubland, hosts many rare and declining species, but most scrub habitat has been lost to development and agriculture. Formerly cultivated sites offer an opportunity to restore Florida scrub. In this 23‐year study, we test whether scrub species could be restored to an old field and whether scrub vegetation composition and structure could be reestablished over time. Scrub oaks were planted in a section of an old field in 1992 after the site was cleared and treated with herbicide. Additional oaks and other scrub species were planted in 1993. We determined survival and growth annually of a marked sample of scrub species. We sampled vegetation cover in two height strata annually on 10 permanent line‐intercept transects in the old grove and on 20 transects in adjacent, intact scrub. Initial survival of Quercus geminata exceeded that of Q. chapmanii or Q. myrtifolia. Cover of scrub oaks greater than 0.5 m increased from 1.3% in 1992 to 65.2% in 2010. However, the vegetation structure of large Q. geminata did not resemble that of native scrub. Adaptive management led to cutting large oaks in the fall of 2010, and burning the site in early 2011. Cutting and burning appeared to stimulate sprouting and clonal spread of scrub oaks. Ordination analysis indicated directional change related to increasing scrub oak cover and time since planting but the old field still differed from intact scrub. Vegetation has developed toward scrub composition and structure but exotic grasses persist.     

Life history,secondary production and population dynamics of <Emphasis Type="Italic">Gammarus fossarum</Emphasis> (Koch, 1836) in a constant temperature stream

Population of the freshwater amphipod Gammarus fossarum was investigated in a calcareous stream with almost constant temperature (7–8°C) in the Chočské Vrchy Mts (West Carpathians, Slovakia). Quantitative samples of G. fossarum taken during 2005 showed population densities varying from 100 m⁻² in August to 585 m⁻² in late November. The population was split into juveniles, mature males, mature females without eggs and females with eggs. The percentage of juveniles (40–64%) was always the highest of any of the categories. Ovigerous females occurred throughout the year. The mean sex ratio was 1: 2.4 (male: female), although its values varied considerably with the time of year. Breeding was continuous, although juvenile recruitment peaked in early spring, summer and early winter. Three discrete cohorts were distinguished from the size frequency distributions. The life span was 6–7 months and the individuals matured approximately in the half of life cycle. The mean fecundity was 9.6 embryos per brood. Variation in fecundity was mostly explained by size of the incubating females. The absolute growth of this species was best described by the Gompertz growth function. Relative growth rates (% body DM day⁻¹) fluctuated in a nonlinear manner with size and age. The highest values of daily growth (2–4% of dry mass per day) were noted approximately in the half of life cycle. Annual production, estimated by the size-frequency method, was 1618.9 g dry mass m⁻² and P/B ratio was 5.15.     

Colonization of leaf patches at topographically different locations by insect shredders in a small mountain stream

We examined physical constraints on the colonization of leaf patches by shredder individuals by comparing the colonizations of artificially standardized leaf patches placed at different locations within a stream reach (i.e., riffles, middles and edges of pools). Stonefly taxa (Nemoura, Protonemura) colonized riffle patches 2–10 times more often than pool (middle, edge) patches, whereas caddisfly taxa (two species of Lepidostoma, Nothopsyche) almost exclusively colonized pool patches. Colonization also differed between the middle and edge patches in pools for most taxa; it was 2–5 times greater in edge patches for Nemoura and in middle patches for Lepidostoma. The abilities of species to cope with low oxygen circulation and high shear stress appear to determine differences in colonization between riffle and pool patches, whereas species-specific dispersion behavior (e.g., return time from drift) may differentiate colonization between middle and edge patches in pools. Our results suggest that changes in leaf distribution within a reach can affect the suitability of stream reaches in terms of food acquisition for shredder individuals.     

Taxonomic Status and Reproduction Dynamics of the Non-Indigenous Cercopagis in the Gulf of Riga (Baltic Sea)

Overwintering population of Cercopagis is represented by resting eggs which hatch generally in May. Although representatives of the first parthenogenetic generation (the spring form individuals) differ morphologically from individuals of the subsequent generations (the summer form individuals) and could be keyed to a separate species – Cercopagis (Apagis) ossiani – our analysis confirm that there is only one Cercopagis species in the Gulf of Riga: Cercopagis pengoi. Notable seasonal dynamics was observed for the gamogenetic mode of reproduction, being strongly associated with the total population density. Gamogenetic females develop since the end of June and reach the maximum absolute abundance in July whereas their proportion is generally the highest in fall. The gamogenetic absolute fecundity drops to the lowest level late July but increased afterwards until the late August. One resting egg was, an average, found in 45.4%, two in 53.4% and three in 1.2% of females. Parthenogenetic fecundity was significantly higher in May–June compared to other months studied. Brood pouch of parthenogenetic females was found to contain 11.6 ± 1.0 and 10.2 ± 0.3 embryos in the spring and summer form individuals, respectively. Variation in the two modes of reproduction and fecundity is probably solely not controlled by temperature, but also by food availability and population density.     

Fire interval effects on persistence of resprouter species in Mediterranean-type shrublands

The capacity of many plant species to resprout in fire-prone shrublands is thought to engender persistence, yet management concerns exist for the long-term persistence of some resprouting species given anthropogenic impacts including shortened fire intervals, long periods of fire exclusion, and/or fires of increasingly high severity. We explored the potential demographic effects of different fire interval regimes on lignotuberous resprouter species using the last fire interval for 36 sites (33 experimental fires, 3 wildfires) in biodiverse SW Australian shrublands, spanning an interval range of 3–42 years. Mortality and regrowth 1 year following the last fire was assessed for >7,000 tagged individuals from 20 shrub and sub-shrub species. Using generalized linear mixed effect models, we estimated the influence of fire interval (and selected fire and environmental covariates) on mortality and regrowth rates across all species, and individually for the four most common species. The overall model, as well as the models for three of the four most common species (Banksia attenuata, Melaleuca leuropoma, and M. systena, but not Hibbertia hypericoides) supported the hypothesis of increased mortality at short and long fire intervals, most likely due to total non-structural carbohydrate (TNC) and bud-bank limitation, respectively. However, no relationship between regrowth rate and fire interval was detected, suggesting that increased mortality at short (3–5 year) fire intervals may not be due solely to resource (TNC) limitation. Results show that lignotuberous resprouters are potentially vulnerable to population decline through attrition of mature plants under both shortened and lengthened fire interval regimes.