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Structure and Dynamics of Lithobates sylvaticus (Wood Frog) at the Periphery of its Range in Missouri
Raymond D. Semlitsch and Dana L. Drake

Southeastern Naturalist, Volume 14, Issue 2 (2015): 329–341

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Southeastern Naturalist 329 R.D. Semlitsch and D.L. Drake 22001155 SOUTHEASTERN NATURALIST 1V4o(2l.) :1342,9 N–3o4. 12 Structure and Dynamics of Lithobates sylvaticus (Wood Frog) at the Periphery of its Range in Missouri Raymond D. Semlitsch1,* and Dana L. Drake1 Abstract - Lithobates (Rana) sylvaticus (Wood Frog) has an extensive distribution primarily in the Appalachian Mountains in the eastern US and throughout Canada and Alaska. However, peripheral populations exist along the southern edge of its range, including in the Ozark regions of Missouri and Arkansas. We present results on the structure and dynamics of 5 Wood Frog populations studied over 4 years (2004–2007) at the edge of the species’ range in central Missouri. We used drift fences and pitfall traps surrounding breeding ponds to sample adults and metamorphosing juveniles. We captured breeding males between 7 February and 13 March, and females between 28 February and 16 March. The sex ratio was male-biased (M:F = 2.4), females were larger than males (mean SVL = 61.3 and 52.3 mm, respectively), and the larval period averaged 14 weeks. The metamorphs had a mean SVL of 18.1 mm and varied in number from 0 to 400 individuals per pond per year. The mean juvenile production per female was 8.7 (range = 0–52), and mean survival from egg to juvenile was 1.28% (range = 0–6.08%). Land managers should consider the species’ small population sizes, low recruitment, survival rates of terrestrial stages, and the interaction of population dynamics with changing climate conditions when planning for conservation of Wood Frog populations at the periphery of the species’ range. Introduction Information on the structure and dynamics of populations is fundamental to understanding how species persist in various locations across their range. Populations at the range periphery can have very different attributes than populations near the range center that can make peripheral populations more susceptible to demographic stochasticity and local extinction (Lesica and Allendorf 1995, Vucetich and Waite 2003). Environmental conditions might be especially limiting outside the center of a species’ distribution (Gaston 1990). Management and conservation decisions are made at landscape and regional levels; thus, an understanding of population dynamics in all parts of a species’ range should inform those decisions. This need may be greatest for conservation in areas at the periphery of species’ ranges where anthropogenic factors such as land use, fragmentation, and climate change might interact with marginal environmental conditions to strongly impact population persistence (Semlitsch 2000). Rana sylvatica LeConte (= Lithobates sylvaticus, Wood Frog) is a widely distributed pond-breeding species that occurs from northern Georgia to Nova Scotia and from Missouri to Alaska (Lannoo 2005, LeConte 1825). Disjunct populations occur along the southern and western edge of its range in Alabama, Arkansas, Colorado, 1Division of Biological Sciences, University of Missouri, Columbia, MO 65211. *Corresponding author - SemlitschR@missouri.edu. Manuscript Editor: Will Selman Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 330 Missouri, Wyoming, Idaho, and possibly South Dakota (Fig. 1; Muths et al. 2005, Trauth et al. 2004). Wood Frogs are typically one of the first species to breed in early spring, are explosive breeders, and use a range of fish-free, seasonal ponds for oviposition (Trauth et al. 2004). Like many other pond-breeding anurans, Wood Frog tadpoles grow rapidly, and juveniles metamorphose during the summer. Both juveniles and adults reside in forested terrestrial habitats surrounding breeding ponds (Rittenhouse and Semlitsch 2007). Although a large number of studies have been conducted on Wood Frogs (cited in Lannoo 2005, Martof and Humphries 1959, Muths et al. 2005), including perhaps the best demographic studies of any amphibian (e.g., Berven 1990, 2009), population studies at the periphery of the species’ range are lacking. Further, a recent study of genetic diversity at the southwestern edge of its range in Missouri indicated that populations of Wood Frogs in a series of isolated conservation areas have reduced genetic variation (Peterman et al. 2013a). Here, we add to knowledge of Wood Frog population biology by providing a detailed account of the structure and dynamics of 5 populations in Missouri studied over a 4-year period. Our objective was to provide information on annual breeding phenology, breeding-population size, sex ratio, adult body size, juvenile emigration, numbers of metamorphosing juveniles, and juvenile body size. We then qualitatively compared our results with those from studies conducted in other parts of the Wood Frog’s range to better understand geographic variation, especially at southern extremes, and to discuss any differences we found in Missouri. Methods Study area We conducted our study within the 1424.5-ha Daniel Boone Conservation Area (DBCA) in the upper Ozark Highlands in Warren County, MO (Fig. 1; Semlitsch et al. 2014). We selected for study 5 breeding ponds located 0.38–1.35 km apart from among >40 available ponds. The 5 ponds we chose are representative and did not differ in obvious ways from all available ponds at DBCA (Fig. 1). The focal ponds were located in mature (80–100 years old), second-growth forest of Quercus sp. (oak) and Carya sp. (hickory) overstory, with varying amounts of Acer saccharum Marsh. (Sugar Maple) in the understory (Semlitsch et al. 2008, 2009, 2014). Approximately equal portions of the forest surrounding each pond were subject to similar levels of timber harvest and subsequently allowed to undergo natural succession (Semlitsch et al. 2009). Our focal ponds were similar in size (high-water area = 160–330 m2), <1.2 m deep, and 27–47 years old. All ponds at DBCA were originally constructed for other wildlife (e.g., Meleagris gallopavo L. [Wild Turkey] and Odocoileus virginianus Zimmermann [White-tailed Deer]) and have been naturally colonized by up to 16 species of amphibians (Hocking et al. 2008). Our 5 study ponds were nearly permanent, fishless, and contained water for the duration of our study except for a short period during a drought late in the summer of 2005. Drift fences and monitoring We completely encircled each breeding pond with a drift fence and pitfall traps during October–December 2003. The drift fences enabled us to sample the Southeastern Naturalist 331 R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 breeding populations and metamorphosing juveniles each year. We constructed the drift fences of aluminum flashing buried ~30 cm into the ground and extending 60 cm above ground (Gibbons and Semlitsch 1982). Pitfall traps consisted of plastic plant pots (23 cm diameter, 45 cm deep) buried so that the top was flush with the ground and the edge was against the fence. Traps were paired along both sides of the fence every 3.0 m. We suspended a wooden board 4 cm above each trap atop metal stakes to reduce predation, and placed a moist sponge in the bottom of each trap to reduce desiccation of trapped animals. Adult Wood Frogs can climb out of pitfall traps (R.D. Semlitsch, pers. observ.), so we assume that we did not detect all individuals. We checked traps every 1–3 days from February to November depending on season of activity and rainfall during 2004, 2005, 2006, and 2007. We recorded trap location, date, sex, age class, and migration direction for all Wood Frogs captured in our traps and released them on the opposite side of the fence. Each year, we also subsampled individuals at each pond and measured body size (snout–vent length [SVL]; mm). Figure 1. Inset map of North America showing the range of Wood Frogs (shaded with open dots) with the position of Daniel Boone Conservation Area (DBCA), Warren County, MO, noted by a black dot. DCBA map showing topographic features and scale is shown with delineated boundary lines in black and a wavy black line through the center showing the only gravel road. All wildlife ponds are indicated with black circles and our study ponds are indicated with X’s in the open circles and labeled as ponds 1–5. Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 332 Our relatively small dataset had substantial variability and was not normally distributed; thus, we performed Kruskal-Wallis tests for all analyses. We tested whether the total number of adults, the number of males, and the number of females varied by pond or year. We also tested whether the mean date of breeding immigration varied by pond or year, as well as whether there was a difference in mean arrival time of males and females. We analyzed whether body size varied between the sexes, whether metamorph number and the mean date of emigration varied among ponds or years, and whether the body size of metamorphs varied with date of emigration. Finally, we correlated the total number of adults captured each year with cumulative rainfall during March as reported for the area in the National Oceanic and Atmospheric Administration climate database, and the total number of metamorphs captured each year with cumulative rainfall during the period 15 May–15 July. All analyses were performed in program R (R Core Team 2013). Results Breeding migrations Male Wood Frogs typically arrived at the ponds earlier than the females, but the date of first capture varied by year (Table 1). The earliest first date of capture for males was 7 February (2005, 2006). The mean first immigration date for males was Table 1. Immigration dates of Wood Frog adults into 5 breeding ponds in Missouri during 2004–2007. A dash (-) indicates no captures were recorded, (n/a) indicates data were not available. Female captures Male captures Juvenile captures Year Pond First Last First Last First Last 2004 1 - - - - - - 2 4 Mar 4 Mar 4 Mar 4 Mar 10 Jun 16 Jun 3 4 Mar 22 Mar 28 Feb 7 Mar 9 Jun 26 Jun 4 - - 3 Mar 8 Mar - - 5 5 Mar 24 Mar 4 Mar 5 Mar - - 2005 1 7 Mar 10 Mar 7 Feb 7 Mar - - 2 28 Feb 7 Mar 7 Feb 7 Mar - - 3 28 Feb 22 Mar 28 Feb 22 Mar 9 Jun 14 Aug 4 8 Mar 31 Mar 28 Feb 12 Apr 15 Jul 15 Jul 5 28 Feb 7 Mar 7 Feb 7 Mar 13 Jul 13 Jul 2006 1 6 Mar 12 Mar 4 Mar 12 Mar - - 2 4 Mar 10 Mar 4 Mar 10 Mar - - 3 6 Mar 12 Mar 6 Mar 6 Mar 30 May 11 Jul 4 6 Mar 12 Mar 4 Mar 10 Mar 12 Jun 12 Jun 5 6 Mar 12 Mar 4 Mar 10 Mar - - 2007 1 - - 1 Mar - - - 2 13 Mar n/a 10 Mar n/a 25 May 31 May 3 10 Mar n/a 1 Mar n/a 23 May 20 Jul 4 16 Mar n/a 10 Mar n/a 31 May 20 Jun 5 - n/a 13 Mar n/a - - Mean 4 Mar 28 Feb 12 Jun Southeastern Naturalist 333 R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 28 February, which was also the earliest first date of capture for females (2005). For Wood Frog females, the mean first date of immigration to the breeding ponds was 4 March, which was significantly later than males (χ2 = 6.51, df =1, P = 0.01). The mean date of immigration of all adults varied significantly between years (χ2 = 12.66, df = 3, P = 0.005), but not between ponds (χ2 = 1.01, df =4, P = 0.91). Mean male immigration date also varied significantly by year (χ2 = 12.85, df = 3, P =0.005), but female immigration rate did not vary by year (χ2 = 4.29, df = 3, P = 0.23). The latest a female and male were captured entering a breeding pond in the spring was 31 March and 12 April 2005, respectively. Although Wood Frogs breed in spring, we captured adult females entering the breeding ponds on 5 October 2004 (n = 1), 24 September 2005 (n = 2), and 1 November 2005 (n = 1). We captured 3 adult males entering breeding ponds on 7 November 2005. However, we found no eggs or tadpoles during the fall. Breeding populations We recorded a total of 116 adult female and 249 adult male Wood Frogs during the 2004–2007 surveys. The number of adults captured varied by pond, sex, and year (Table 2), but the only statistical difference was in the number of males among years (χ2 = 14.41, df = 3, P = 0.002) and the number of adults by year (χ2 = 11.97, df = 3, P = 0.007). Other comparisons of adults included total number (χ2 = 0.37, df = 4, P = 0.98), number of males (chi-square = 0.313, df =4, P = 0.99), and Table 2. Breeding-population sizes for females and males, sex ratios, the number of emigrating juveniles (metamorphs), ratios of juveniles to females, and egg to metamorphosis survival of Wood Frogs at 5 breeding ponds in Missouri during 2004–2007. Egg to metamorphosis survival (survival/egg) was calculated using a mean clutch size of 850 eggs per female Wood Frog (Trauth et al. 2004). Year Pond Females (n) Males (n) Ratio (M:F) Metamorphs Meta: Female Survival/egg 2004 1 0 0 0.00 0 0.00 0.0000 2 3 5 1.67 7 2.33 0.0027 3 9 9 1.00 195 21.67 0.0250 4 0 2 0.00 0 0.00 0.0000 5 3 4 1.33 0 0.00 0.0000 2005 1 4 14 3.50 0 0.00 0.0000 2 29 42 1.45 0 0.00 0.0000 3 11 24 2.18 218 19.82 0.0229 4 1 7 7.00 3 3.00 0.0035 5 30 40 1.33 1 0.03 0.0000 2006 1 9 13 1.44 0 0.00 0.0000 2 17 32 1.88 0 0.00 0.0000 3 10 3 0.30 400 40.00 0.0461 4 6 13 2.17 1 0.17 0.0002 5 14 18 1.29 0 0.00 0.0000 2007 1 0 8 0.00 0 0.00 0.0000 2 2 19 9.50 41 20.50 0.0236 3 9 24 2.67 314 34.89 0.0402 4 4 14 3.50 4 1.00 0.0012 5 0 5 0.00 0 0.00 0.0000 Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 334 number of females (χ2 = 1.77, df = 4, P = 0.78), none of which showed statistically significant differences among ponds. Annual differences in the number of females also did not differ (χ2 = 5.57, df =3, P = 0.13). Ponds 1 and 4 had the fewest adults during our study (n = 36 and 74, respectively), and ponds 2 and 5 had the most (n = 88 each), with ranges as low as 0 (pond 1 in 2004) and as high as 57 (pond 5 in 2005) total adults at a pond. We captured a mean of 7.25 (range = 0–22) female Wood Frogs and a mean of 13.1 (range = 0–35) male Wood Frogs per pond over the 4 years. We captured the fewest adult Wood Frogs (n = 24) during the first year of sampling (2004), but then collected the most (n = 190) in 2005, with numbers decreasing in subsequent years. We captured no females or males at pond 1 in 2004 and no females at ponds 1 and 4 in 2004 or ponds 1 and 5 in 2007. The total number of adults captured in drift fences was negatively correlated with the cumulative amount of rainfall during March (Spearman’s rho = -0.79, P < 0.001). We detected sexual dimorphism in SVL between breeding adults: females were larger than males (mean SVL = 61.3 mm ± 6.6 SD [n = 102] and 52.3 mm ± 3.7 SD [n = 221], respectively; Kruskal-Wallis chi-square = 180.1, df = 1, P < 0.0001; Fig. 2). The smallest breeding female was 42 mm SVL, and the smallest breeding male was 41 mm SVL. The sex ratio of females to males was primarily male biased, with the exception of pond 3 in 2004 and 2006 (Table 2). The mean ratio of males to females at all ponds over all years was 2.4 to 1. Juveniles emigrating We captured a total of 1184 juvenile Wood Frogs emigrating from all ponds during all years. The number of metamorphs varied significantly among ponds (χ2 = 8.05, df = 3, P = 0.045), but not among years (χ2 = 0.48, df = 3, P = 0.92). The total number of metamorphs captured in drift fences was not correlated with cumulative rainfall during 15 May–15 July (Spearman’s rho = 0.04, P = 0.84). The earliest capture of emigrating juveniles occurred on 23 May 2007, and the average date of emigration was 12 June. Differences in the average date of juvenile emigration were not statistically significant among ponds (χ2 = 2.30, df = 3, P = 0.51) but were significant among years (χ2 = 8.00, df = 3, P = 0.046). Based on the average date of arrival of breeding females at the ponds and the average date of juvenile emigration, we calculated the larval period to be ~14 weeks. We captured a few juveniles leaving the ponds in July and August, with a latest date of capture on 14 August (2005). We measured the body size of 609 metamorphs during the survey period. The smallest metamorph was 14 mm SVL (pond 3, 31 May 2006, n = 2), and the largest 2 metamorphs were 29 and 26 mm SVL (9 June 2004 and 11 July 2006, respectively). The total mean SVL of all metamorphs measured was 18.1 mm ± 1.43 SD (Fig. 3). The size at metamorphosis was largest in 2007 and smallest in 2006 (mean SVL of 20 mm and 17.8 mm, respectively). The mean metamorph size was highest at pond 2 (21.3 mm SVL) and lowest at pond 3 (18 mm SVL). The body size of metamorphs was slightly larger the later in the summer they emigrated from ponds (Spearman’s rho = 0.069, P = 0.0001). Southeastern Naturalist 335 R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 Juveniles metamorphosed out of 4 of the 5 ponds; we captured only one metamorph in pond 5 in all years (Table 2). Pond 3 had the highest juvenile output of all of the ponds sampled (95.2% of total coming out of all ponds), but was not the pond with the highest number of breeding adults captured. Juvenile production was higher for all ponds in 2006 and 2007 than in 2004 or 2005. Calculating survival through metamorphosis based on average clutch-size per female (850 eggs; Trauth et al. 2004) revealed that over 4 years, ponds had a mean larval survival of 1.28% and a maximum survival of only 6.07% (Table 2). Discussion The Wood Frog is one of the most widely distributed amphibian species in North America, with a range covering the northeastern US, and most of Canada Figure 2. Size-frequency distribution of snout–vent length (SVL) of adult Wood Frogs captured at 5 breeding ponds in Missouri during 2004–2007. Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 336 and Alaska (Lannoo 2005). Although large populations can be found in the northern portion of its range (Berven 2009, Egan and Paton 2004), populations along the southern and western edges are small and fragmented, which makes them more susceptible to habitat loss and fragmentation due to altered land use (Muths et al. 2005). Wood Frogs in Missouri have a basic life history similar to that observed in most other regions across its range; however, because their populations there are isolated and considered vulnerable, the species is listed as being of conservation concern (Missouri Natural Heritage Program 2007). We found that breeding migrations started in late February and ended by the middle of March each year, typically lasting no more than 2 weeks. Males usually arrived earlier than females, with the onset of breeding for males among the earliest reported (7 February) compared to other southern regions (Maryland: 15 February [Berven 1982], Tennessee: 22 February [Meeks and Nagel 1973], eastern Missouri: Figure 3. Size-frequency distribution of snout–vent length (SVL) of Wood Frog metamorphs captured leaving 5 ponds in Missouri during 2004–2007. Southeastern Naturalist 337 R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 26 February [Guttman et al. 1991]). The onset of breeding is largely determined by rainfall and increasing spring temperatures; thus, annual variation of environmental factors in Missouri likely accounts for these differences. Meeks and Nagel (1973) noted that temperatures that trigger breeding migrations (>5–6 °C) appeared to be similar across the Wood Frog’s range, suggesting that breeding period varies with the date at which critical temperatures are reached at each population location. The breeding-population sizes of Wood Frogs were small at our study sites in Missouri compared to populations in the central portion of the species’ range. In other regions, breeding population sizes were >500 adult frogs in most years in Maryland (Berven 1990), up to 1033 females in Rhode Island (Egan and Paton 2004), and in some years exceeded 6000 adults in Michigan (Berven 2009). However, we found only a few males and females in some years and at most just 30 females and 42 males. The number of breeding adults fluctuated greatly, and in 2004 and 2007, we collected no females at 2 different ponds. We likely did not detect all Wood Frogs because they are known to escape from pitfall traps (R.D. Semlitsch, pers. observ.), so the actual number of adults present may have been higher. However, egg-mass counts at these ponds in subsequent years and at the other surrounding ponds at DBCA also indicated low numbers of females (Peterman et al. 2013b). In addition, we found that the number of adults we captured was negatively correlated with cumulative rainfall during the breeding period. Although this is counter-intuitive, we suggest that moisture for terrestrial migration in the spring is not limiting, so more rainfall would unlikely cause more frogs to breed. Therefore, we posit that more rainfall may create additional temporary pools (in road ruts and ditches) that draw adults away from the more permanent wildlife ponds. We found that adult body size averaged 52.3 mm and 61.3 mm for males and females, respectively, and their size was very similar to results reported in another study in eastern Missouri (51.1 mm and 60.3 mm for males and females, respectively; Guttman et al. 1991). The smallest Wood Frog body sizes were reported in Canada, averaging 37.7 mm for males and females combined in Manitoba and Saskachewan (Martof and Humphries 1959) and 47.1 mm and 50.9 mm for males and females, respectively, in northern Quebec (LeClair et al. 2000). Some of the largest Wood Frogs were found in the mountains of Virginia (55.3 mm and 64.4 mm for males and females, respectively; Berven 1982) and in the mountains of Georgia and North Carolina (54.8 mm and 66.8 mm for males and females, respectively; Martof and Humphries 1959). Thus, the number of females contributing to reproduction was likely limited rather than the absolute contribution per female, which is determined primarily by body size (i.e., larger females produce more eggs; Berven 1990). Our results showed that the number of metamorphosing juveniles also fluctuated widely among ponds and years, with most ponds producing no metamorphs, while 1 pond produced at least 400 metamorphs. Rainfall during the period of emigration had no apparent correlation with the number of metamorphs captured at our drift fences. At our sample ponds, survival rate from the egg stage to metamorphosis averaged 1.28% among years with the most successful pond having Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 338 6.07% survival to metamorphosis in one year. This single pond produced 195–400 metamorphs each year and contributed 95% of all the metamorphs that had the potential to be recruited into adult breeding populations. Berven (1990) reported larval survival from Maryland ponds averaged 0.95–4.5% with a maximum survival rate of 8% in one year. Most ponds at the DBCA are small and nearly permanent, seldom drying seasonally. These permanent ponds are numerically dominated by 4 predatory salamander species (Drake et al. 2015, Hocking et al. 2008), including Ambystoma opacum (Gravenhorst) (Marbled Salamander) and A. annulatum (Cope) (Ringed Salamander). Larvae of salamanders that breed in the fall likely prey heavily on newly hatched, spring-breeding Wood Frogs. Adult Notophthalmus viridescens (Rafinesque) (Eastern Newt) are also present in early spring (R.D. Semlitsch, pers. observ.; Trauth et al. 2004) and may prey heavily on hatchling Wood Frogs. More-permanent ponds also have a high density and diversity of invertebrate predators that prey on tadpoles (Shulse et al. 2013). Therefore, predation and quality of the aquatic habitat in permanent wildlife ponds may be important for predicting Wood Frog success at our study sites. We found that the body size of metamorphosing juveniles in our study averaged 18.1 mm and was comparable to the larger metamorphs observed in Virginia. Berven (1982) found that metamorphosing juveniles were larger in mountain ponds of Virginia (averaged 17.8, 19.3, and 19.4 mm across 3 years) than in lowland ponds of Maryland (averaged 14.9, 14.2, and 15.6 mm). Further, the larval period for tadpoles in Missouri is approximately 98 days and falls in the middle of development times reported across the species’ range (60–120 days; Martof and Humphries 1959). Therefore, the metamorphs leaving our ponds appeared to attain a comparatively large body size in a moderate period of time, both of which are traits that should favor higher survival in the terrestrial habitat (Berven 1982, 1990; Harper 2007). We found small population sizes at our 5 study ponds and believe these ponds were representative of others in the DBCA. Peterman et al. (2013a) found low numbers (mean = 10 ± 5.12 clutches per pond per year) of Wood Frog egg masses during 6 years of surveys in all 34 ponds occupied at DBCA. These results indicate that breeding-population sizes at DBCA are consistently small, a finding in line with observations from 2 adjacent conservations areas (Peterman et al. 2013b) and thus suggests this is a general trend at the southwest edge of the species’ range in Missouri. No data are available from other peripheral Wood Frog populations to make more quantitative comparisons. It is unclear whether small population size is due to low production of metamorphosing juveniles and predation in permanent ponds or low juvenile and adult survival in terrestrial habitat or both. The habitat at DBCA is high-quality mature forest and very suitable for other species like fossorial Ringed Salamanders (e.g., Semlitsch et al. 2014); however, rainfall in the upper mid-western US is relatively low and results in occasional droughts that can significantly affect survival of the terrestrial stages primarily due to physiological stress (Harper 2007, Rittenhouse et al. 2009). The ecological drivers of terrestrial survival warrant future study. Southeastern Naturalist 339 R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 Our findings highlight the need to develop a management plan to ensure the long-term persistence of Wood Frogs in Missouri. Although several areas within Missouri have remnant Wood Frog populations (including conservation areas in the Riverhills Region east of DBCA and further southwest in the Ozark Highlands of Missouri and northwestern Arkansas), these areas are disjunct from the major portion of the species’ range east of the Mississippi River (Fig. 1). Further, although they were not documented, historical Wood Frog breeding sites were likely in locations along the bluffs of the Missouri River floodplain that have largely been converted to agriculture. Thus, to maintain remnant populations in Missouri, we suggest that further habitat analyses are needed to understand how aquatic pond habitats and the terrestrial habitat surrounding ponds can be improved to increase survival in each Wood Frog life-history stage (Semlitsch 2000). The addition of seasonal ponds that dry each year and reduce the risk of predation by predatory salamanders seen in most permanent ponds at DBCA may be necessary to increase production of juveniles. New ponds should be interspersed among existing ponds that already produce good numbers of egg clutches to promote colonization by adults (Peterman et al. 2013b). Maintaining adequate terrestrial core habitat of mature forest surrounding each breeding pond (~300–500-m radius) that also includes ravines for over-summer habitat would help protect juveniles and adults, especially in drought years (Harper et al. 2008, Rittenhouse and Semlitsch 2007:fig. 2C, Rittenhouse et al. 2009). Further, considering that low genetic variation has been documented at 1 of the most-distant conservation areas occupied by Wood Frogs (Danville Conservation Area ~10–12 km northwest of DBCA; Peterman et al. 2013a), it seems important to incorporate plans to increase connectivity and re-establish gene flow across the region and among adjacent conservation areas inhabited by Wood Frogs. If peripheral populations of species such as Wood Frogs are to be maintained, then development of effective plans and active management are likely needed to keep potentially important populations such as these from going locally extinct. Acknowledgments We thank S. Altnether, T. Altnether, C. Conner, J. Earl, E. Harper, D. Hocking, M. Osbourn, D. Patrick, L. Rehard, T. Rittenhouse, B. Scheffers, J. Sias, and E. Wengert for building drift fences and checking pitfall traps; T. Anderson for analyses; and J. Briggler and G. Raeker of the Missouri Department of Conservation for permits and logistical support. This research was supported by a collaborative grant from the National Science Foundation DEB 0239943 and from the Department of Defense SERDP grant RC-2155 to R.D. Semslitsch. Animals were sampled under University of Missouri Animal Care and Use Protocol 3368. Literature Cited Berven, K.A. 1982. The genetic basis of altitudinal variation in the Wood Frog, Rana sylvatica. II. An experimental analysis of larval development. Oecologia 52:360–369. Berven, K.A. 1990. Factors affecting population fluctuations in larval and adult stages of the Wood Frog (Rana sylvatica). Ecology 71:1599–1608. Southeastern Naturalist R.D. Semlitsch and D.L. Drake 2015 Vol. 14, No. 2 340 Berven, K.A. 2009. Density dependence in the terrestrial stage of Wood Frogs: Evidence from a 21-year population study. Copeia 2009:328–338. Drake, D.L., B.H. Ousterhout, C.D. Shulse, D.J. Hocking, W.E. Peterman, T.L. Anderson, K.L. 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