Reproductive biology of Rioraja agassizi from the coastal southwestern Atlantic ecosystem between northern Uruguay (34°S) and northern Argentina (42°S)

A total of 552 individuals of Rioraja agassizi (257 females and 295 males) were collected by bottom-trawl during research cruises. Sexual dimorphism was observed with females are heavier than males for a given total length (TL). Using logistic regression, it was determined that TL at 50% maturity of males was 475 mm TL and of females 520 mm TL. This estimation agrees with the morphological parameters measured. Although not statistically significant, a peak in reproductive activity was observed in males during late spring and summer. The monthly variation in the gonadosomatic index and oviducal gland width, together with the largest diameter of ovarian follicles, suggests that R. agassizi females have a partially defined annual reproductive cycle with two peaks, one from November (spring) to February (summer) and another in July (winter).     

Reproductive biology of Philodryas patagoniensis (Snakes: Dipsadidae) in south Brazil: Female reproductive cycle

In this study, we describe the female reproductive cycle of Philodryas patagoniensis in south Brazil, which was described through morpho‐anatomical and histological analyses. The peak of secondary vitellogenesis occurred during winter–spring (July–December), ovulation in spring (October–December), mating and fertilization in spring–summer (October–February), oviposition in spring–autumn (October–May) and births from late spring to autumn (December–July). The diameter of vitellogenic follicles/eggs was larger in winter–spring than in other seasons. The diameter of the shell glands was also larger in winter–spring. In spite of the clear reproductive peak, gonads only showed reduced activity in the autumn. Therefore, at the individual level, females have a discontinuous cyclical reproduction; in the populational level, the reproductive cycle is seasonal semisynchronous. We support the hypothesis that P. patagoniensis have the ability to produce multiple clutches with long‐term stored sperm. Sexual dimorphism in body size was evident, and females are significantly larger and heavier than males. Larger females were able to produce follicles and eggs in larger amount and size. The maternal body size was positively related to the reproductive effort and fecundity. To conclude, we deliberated about the proximal and distal causes that influence the reproductive traits and patterns of P. patagoniensis.     

Assessing the role of body mass and sex on apparent adult survival in polygynous passerines: a case study of cetti's warblers in central Portugal

Adult survival, an important fitness component, is usually 1) lower in lighter individuals due to their reduced ability to survive winter conditions compared to heavier ones, especially in resident species at northern temperate latitudes and 2) lower in females compared with males due to higher reproductive costs incurred by females. In this paper, a capture–mark–recapture dataset of 649 cetti's warblers Cettia cetti ringed seasonally at two wetlands in central Portugal over an 11‐yr period (2000–2010) was modelled in a multi‐state framework to examine the influence of these individual covariates on apparent adult survival, while controlling for the presence of transient individuals in our study area. The probability of change in mass state (ψ_{Light→Heavy}, ψ_{Heavy→Light}) during the annual cycle was also estimated. Overall, birds survived better during spring–summer (breeding/moulting periods) compared with autumn–winter, but there was no effect of body mass on apparent adult survival probability. The modelling detected a significant interaction between sex and season, in which resident females survived better than resident males in spring–summer (?_RF= 0.857 ± 0.117 and ?_RM= 0.698 ± 0.181) while the opposite pattern was found in autumn–winter (?_RM= 0.440 ± 0.086 and ?_RF= 0.339 ± 0.084). In addition, cetti's warblers had a tendency to lose mass in spring–summer (ψ_{Heavy → Light}= 0.560 ± 0.063) and to regain mass in autumn–winter (ψ_{Light→Heavy}= 0.701 ± 0.069). This pattern of body mass change during the annual cycle may reflect energetic costs to reproduction and moulting, and/or a response to increased starvation risk during winter. High body mass, however, did not increase adult survival in this population presumably due to the relatively mild winter weather prevailing in central Portugal. Survival estimates are more likely to be explained by important ecological and behavioural differences between the two sexes in polygynous passerines. Our results highlight that studies aiming to identify the main factors shaping survival and individual fitness in polygynous species should be conducted during different phases of their annual cycle.     

Reproductive cycle of seabob shrimp Xiphopenaeus kroyeri (Crustacea,Penaeidea) from the northeast coast of Brazil

The reproductive cycle of Xiphopenaeus kroyeri north-eastern Brazil was described to contribute to the sustainable management of this stock in the region. Specimens were collected monthly from August 2011 to July 2012 using a local vessel of the artisanal fleet. A total of 1201 individuals were analyzed (673 females and 528 males) with a mean carapace length (CL) of 1.88 ± 0.16 cm and total length (TL) of 9.00 ± 1.22 cm. The lowest CL and TL of mature females were 1.33 and 6.5 cm, respectively, and all females above 2.44 cm (CL) and 11.5 cm (TL) were mature. Ovarian maturation was classified into four stages: I (immature), II (maturing), III (mature) and IV (spawned). Individuals of all maturational stages were present throughout the year. Considering the macro and microscopic analysis, it was suggested that this species in north-eastern Brazil has a continuous reproductive cycle, with two seasonal peaks, November/December and February (austral spring and summer). A positive correlation between the percentage of mature females and temperature was observed, and a higher percentage was reported in the warmer months of the year. This suggests that the reproductive peaks can be triggered by water temperature variation throughout the year.     

Spatial variation in the annual reproductive cycle of Turbo (Batillus) cornutus (Gastropoda: Trochidae) at Jeju Island,Korea

The annual reproductive cycle of the top shell Turbo cornutus from Jeju Island was investigated in two populations using histology. In the northern population, gametogenesis commenced in January as the surface water temperature reached 14?°C, while in the southern population gametogenesis began a month earlier, as the water temperature remained at 17?°C. Ripe top shells first appeared in June and spawning continued from June to October when water temperatures were between 20 and 24?°C. Histology indicated that the spawning period of the southern population was a month earlier and lasted longer (June–October) than in the northern population (July–September). The percentage gonad area of animals in the southern population in March and April was significantly higher than in the northern population (p?相似文献   

Sex steroids, growth and condition of Arctic charr broodstock during an annual cycle

Changes in plasma concentrations of sex steroids, growth rate and condition of repeat spawning (3+) male and female Arctic charr were studied throughout an annual reproductive cycle. Individually marked fish (mean weight approx. 500 g) were held under conditions of liberal food supply, constant temperature (4° C) and simulated natural photoperiod (Tromsø, 70° N). Once each month fish were weighed, measured and blood samples taken for steroid analysis. Plasma concentrations of testosterone (T), 11-ketotestosterone (11-KT) and oestradiol-17β (E₂) were determined using radioimmunoassay (RIA). Both male and female fish displayed distinct seasonal changes in plasma concentrations of sex steroids, growth rate and condition. From February (minimal concentrations) to March all sex steroids increased slightly and these elevated concentrations were maintained until May. Thereafter, there was a second, and far more pronounced, increase in plasma steroid concentrations which culminated in peak steroid concentrations in September–October. There was then a rapid decline during the spawning period. In winter, growth rate and condition were generally low, then increased during the spring, reached a peak during the summer, and then declined with the onset of autumn. During spring (March–May), the frequency distributions of plasma testosterone concentrations in both male and female fish were bimodal. The fish of the upper modal group of the distribution had significantly higher growth rates and condition than those in the lower modal group. In summer and early autumn (June–September) the association between T and growth rate changed. Significant negative correlations between T and growth rates were observed in females. There was an increase in endocrine activity, indicated by elevated plasma sex steroid concentrations in March, 7–8 months prior to maturation. It is suggested that this may be one factor influencing the onset of spring growth and energy deposition among maturing charr.     

Life history, aspects of reproductive biology and production of Corophium orientale (Crustacea: Amphipoda) in Monolimni lagoon (Evros Delta, North Aegean Sea)

Monthly samples of Corophium orientale were collected during February 1998–February 1999 in both parts of Monolimni lagoon (0.3 < Sal. < 6 psu, 2 < Temp. < 28.5 °C). Corophium orientaleshowed a semiannual life cycle. In the southern part, breeding occurred from early spring to mid autumn having three peaks, in early spring, early summer and early autumn, and three cohorts were produced, a spring cohort, a summer cohort and an overwintering one. In the shallower innermost northern part of Monolimni lagoon, breeding peaked in mid-spring and, also, in early autumn, and two discrete cohorts, a spring and an overwintering one, were produced. A lack of large individuals, attributed to a temporary size – selective predation by migrating shorebirds, was observed during summer. That lack possibly contributed to the hiatus in reproduction. Photoperiod seemed to be a more important cue than temperature in the initiation of the reproductive cycle, while extremely low salinities (<1 psu) did not deter breeding. Females attained maturity at a smaller size in late spring and, especially, in summer than in early spring at lower temperatures. Brood size was a function of females body size. Females, matured during summer at high temperatures, showed the lowest brood size, body length ratio. Mean brood size was small (12–13 early embryos) and embryo loss during development high (54%), possibly due to a negative effect of low salinities. A 1:1 sex ratio existed in the small body length classes, but females preponderated in the large ones. The spring cohort in the southern part, which developed at moderate temperatures, showed the highest growth rate (40 m day^–1). Secondary production of C. orientalecalculated by Hyness method gave a mean annual density of 4562.5 and 9327.6 ind. m^–2, a mean annual crop (B) of 1.03 and 2.67 g DW m^–2, an annual production (P) of 6.91 and 22.54 g DW m^–2 and a P/B ratio of 6.7 and 8.4 in the northern and southern part of the lagoon, respectively.     

Reproductive biology of the sand dollar,Peronella lesueuri (L. Agassiz, 1841) (Echinoidea: Clypeasteroida: Laganidae), in south-western Australia

The reproductive biology of the sand dollar Peronella lesueuri was studied between 2009 and 2011 in Cockburn Sound, a large coastal embayment in south-western Australia. Individuals of P. lesueuri did not display sexual size-dimorphism, and the population was found to have a sex ratio of 1:1. Maturity occurred over the range of 80–115 mm with all sand dollars larger than 115 mm having distinct gonads. Monthly histological analysis of gonads and changes in oocyte proportions over time indicated that P. lesueuri has an annual reproductive cycle; gametogenesis occurs in spring and spawning in summer. Differences in the rate of gametogenesis between 2009/2010 and 2010/2011 may have been influenced by higher temperatures experienced in 2010/2011. P. lesueuri have large ova (mean?=?210 μm), which suggests the species has lecithotrophic larval development.     

The reproductive cycle of the male sleep snake Sibynomorphus mikanii (Schlegel, 1837) from southeastern brazil

This study describes the male reproductive cycle of Sibynomorphus mikanii from southeastern Brazil considering macroscopic and microscopic variables. Spermatogenesis occurs during spring–summer (September–December) and spermiogenesis or maturation occurs in summer (December–February). The length and width of the kidney, the tubular diameter, and the epithelium height of the sexual segment of the kidney (SSK) are larger in summer–autumn (December–May). Histochemical reaction of the SSK [periodic acid‐Schiff (PAS) and bromophenol blue (BB)] shows stronger results during summer–autumn, indicating an increase in the secretory activity of the granules. Testicular regression is observed in autumn and early winter (March–June) when a peak in the width of the ductus deferens occurs. The distal ductus deferens as well as the ampulla ductus deferentis exhibit secretory activities with positive reaction for PAS and BB. These results suggest that this secretion may nourish the spermatozoa while they are being stored in the ductus deferens. The increase in the Leydig cell nuclear diameter in association with SSK hypertrophy and the presence of sperm in the female indicate that the mating season occurs in autumn when testes begin to decrease their activity. The peak activity of Leydig cells and SSK exhibits an associated pattern with the mating season. However, spermatogenesis is dissociated of the copulation characterizing a complex reproductive cycle. At the individual level, S. mikanii males present a continuous cyclical reproductive pattern in the testes and kidneys (SSK), whereas at the populational level the reproductive pattern may be classified as seasonal semisynchronous. © J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Reproductive cycle and spatiotemporal variation in abundance of the one-sided livebearer Jenynsia multidentata, in Patos Lagoon, Brazil

Jenynsia multidentata is an important component of the fish assemblage of the Patos Lagoon estuary in southern South Brazil. In order to investigate its reproductive cycle and abundance patterns, standardized sampling was conducted over large spatial (marine, estuary and lagoon) and temporal (1996–2003) scales. Both females and males were significantly more abundant during summer (December–March) than winter (June–August). Total abundance was significantly positively correlated with water temperature (R=0.91), but not with salinity and Secchi depth. Females achieved higher average (49.1 mm L _T) and maximum size (91 mm) than males (37.7 mm; 66 mm), and average sex ratio was female-biased (3.2:1) across all months. An annual reproductive cycle composed of two cohorts was proposed: individuals born from December to March started reproducing during late winter and spring and individuals born from September to November started reproducing during late summer and fall. A 12-month survey conducted throughout the longitudinal gradient of the lagoon indicated that the species was only present in the estuary, and was absent from marine and upper lagoon areas. The abiotic factors analyzed could not explain this spatial distribution. Inter-annual variation in abundance was great, with higher abundance during drier years. A `dilution effect' was proposed to explain the low abundance of the species in the estuary during high-rainfall trigged by El Niño episodes.     

Reproductive cycle of the winged pearl oyster,Pteria penguin (Röding 1793) (Pteriidae) in north-eastern Australia

The spawning cycle of the winged pearl oyster, Pteria penguin, was studied at Orpheus Island, north-eastern Queensland to observe seasonal changes in gonad development, mean oocyte diameter and sex ratio over time. A total of 201 oysters were collected over 10 sampling periods, approximately every 5–6 weeks (mean?=?20 oysters/sample). Histological analysis of gonads showed that spawning activity occurred mainly through the austral mid-spring to late summer (November to March), when mean monthly water temperature ranged between 27.5°C and 29.4°C. There was a primary spawning peak at the beginning of the spawning season in December, followed by a secondary peak in March. Mean oocyte diameter (µm) was highest during the warmer months, ranging from 31.2?±?2.4 in November to 36.2?±?3.2 in March, and sex ratio analysis showed the percentage of females in the population also peaked between 30% and 50% during this period.     

Population structure,recruitment, and mortality of the freshwater crab Dilocarcinus pagei Stimpson, 1861 (Brachyura,Trichodactylidae) in Southeastern Brazil

Freshwater crabs of the family Trichodactylidae are widely distributed in major river basins of the South American continent. The population structure of one species, Dilocarcinus pagei, was analyzed in an artificial reservoir in Southeastern Brazil, recording data on the sex ratio, recruitment, and mortality. A total of 1339 crabs were collected and included 804 males and 535 females (3 ovigerous and 4 with hatchlings); the sex ratio was 1:0.61 (males: females). Two modes of male and female carapace width (CW) were recorded, with means of 14.4 mm (n = 407) and 38.9 mm (n = 394) for males and 17.9 mm CW (n = 269) and 39.2 mm (n = 267) for females. The mean size of males (CW = 26.6 ± 13.8 mm) was significantly larger than that of females (CW = 28.5 ± 12.8 mm). The data indicated that recruitment occurs in summer (January–March), with the reproductive period in spring (October–December), periods with the highest rainfall and temperature values in the region. Reproduction leads to the death of the parents, influencing the sex ratio, which oscillates mainly during the reproductive period.     

Influence of season and body condition on plasma volume levels of white‐tailed deer,Odocoileus virginianus

Abstract

Changes in the circulating plasma volume were monitored for twelve consecutive months in five white‐tailed deer (Odocoileus virginianus) maintained outdoors in a 2.4‐ha enclosure in northern New York stale. The mean annual relative plasma volume of the two male white‐tailed deer (43.6 ± 1.0 ml/kg) was not significantly different from that of three females (45.7 ± 0.7 ml/kg). Mean annual absolute plasma volume, however, was significantly higher in males (2588 ± 90.7 ml) than in females (2092 ± 79.1 ml), mainly because of the greater body weights of males in late summer and early fall. Both sexes had a marked seasonality in the level of relative and absolute plasma volume regulation. Relative plasma volumes were lowest in February‐March and highest in May‐June and again in October, while absolute plasma volumes were lowest in late winter to early spring, when body weights in the annual cycle were lowest, and volumes were highest in mid‐fall, at the annual peak of body condition. Males had a greater excursion about their annual mean relative plasma volumes (‐16 to 13%) and absolute plasma volumes (‐23 to 32%) than did females (respectively, ‐11 to 9% and ‐13 to 19%). Variations in the level of plasma volume regulated are related to the annual cycle of environmental conditions and changes in body and physiological condition of white‐tailed deer.     

The reproductive biology of an endemic cyprinid,Zacco pachycephalus,in Taiwan

Synopsis Reproductive parameters including body weight-length relationship, condition factor, gonadosomatic index (GSI) and fecundity of an endemic cyprinid,Zacco pachycephalus, were studied from October 1991 to January 1993. Although the condition factor was similar between both sexes, GSI values of female (3.72 to 14.24%) were significantly larger than that of males (0.21 to 2.23%) during the major breeding season. The number of yolky eggs per fish ranged from 459 to 2059. Ovum size distribution, annual GSI value, and recruitment of juvenile fish indicated thatZ. pachycephalus conducted two major spawning activities in spring (February to April) and summer (June to August). The larger GSI value and number of yolky eggs in spring compared to those in summer implies thatZ. pachycephalus has evolved a reproductive style by investing more energy in spring to avoid the damage of summer freshet on its recruitment success. The mating behavior ofZ. pachycephalus is similar to that of otherZacco fishes.     

Assessing Toxicant Effects in a Complex Estuary: A Case Study of Effects of Silver on Reproduction in the Bivalve,Potamocorbula amurensis,in San Francisco Bay

Contaminant exposures in natural systems can be highly variable. This variability is superimposed upon cyclic variability in biological processes. Together, these factors can confound determination of contaminant effects. Long term, multidisciplined studies with high frequency sampling can be effective in overcoming such obstacles. While studying trace metal contamination in the tissues of the clam, Potamocorbula amurensis, in the northern reach of San Francisco Bay, an episode of high Ag concentrations was identified (maximum of 5.5?µg g^?1) at two mid-estuary sites. High concentrations were not seen in clams up-estuary (maximum of 1.92?µg g^?1) from these sites and were reduced down-estuary (maximum of 2.67?µg g^?1). Silver is not common naturally in the environment, so its elevated presence is usually indicative of anthropogenic influences such as municipal and industrial discharge. Monthly sampling of reproductive status of clams characterized the reproductive cycle and differences in the patterns of reproductive activity that corresponded to changes in Ag tissue concentrations. The proportion of reproductive clams was less than 60% during periods when tissue concentrations were high (generally >2?µg g^?1). When tissue concentrations of Ag decreased (≤1?µg g^?1), the proportion of reproductive clams was 80 to 100%. A comparison between the annual proportion of reproductive clams and annual Ag tissue concentrations showed a significant negative correlation. No other measured environmental variables were correlated with reproductive impairment. The weight-of-evidence approach strongly supports a cause and effect relationship between Ag contamination and reduced reproductive activity in P. amurensis.     

Melatonin in the Regulation of Annual Testicular Events in Carp Catla catla: Evidence from the Studies on the Effects of Exogenous Melatonin,Continuous Light,and Continuous Darkness

The physiological significance of melatonin in the regulation of annual testicular events in a major carp Catla catla was evaluated through studies on the effects of graded dose (25, 50, or 100 µg/100 g body wt.) of melatonin exogenously administered for different durations (1, 15, or 30 days) and manipulation of the endogenous melatonin system by exposing the fish to constant darkness (DD) or constant light (LL) for 30 days. An identical experimental schedule was followed during the preparatory (February–March), pre‐spawning (April–May), spawning (July–August), and post‐spawning (September–October) phases of the annual cycle. Irrespective of the reproductive status of the carp, LL suppressed while DD increased the mid‐day and mid‐night values of melatonin compared to respective controls. Influences of exogenous melatonin varied in relation to the dose and duration of treatment and the reproductive status of the carp. However, testicular response to exogenous melatonin (at 100 µg, for 30 days) and DD in each reproductive phase was almost identical. Notably, precocious testicular maturation occurred in both DD and melatonin‐injected fish during the preparatory phase and in LL carps during the pre‐spawning phase. In contrast, testicular functions in both the melatonin‐treated and DD fish were inhibited during the pre–spawning and spawning phases, while the testes did not respond to any treatment during the post‐spawning phase. In conclusion, this study provided the first experimental evidence that melatonin plays a significant role in the regulation of annual testicular events in a sub‐tropical surface‐dwelling carp Catla catla, but the influence of this pineal hormone on the seasonal activity of testis varies in relation to the reproductive status of the concerned fish.     

Annual variation in soil respiration and its components in a coppice oak forest in Central Italy

In order to investigate the annual variation of soil respiration and its components in relation to seasonal changes in soil temperature and soil moisture in a Mediterranean mixed oak forest ecosystem, we set up a series of experimental treatments in May 1999 where litter (no litter), roots (no roots, by trenching) or both were excluded from plots of 4 m². Subsequently, we measured soil respiration, soil temperature and soil moisture in each plot over a year after the forest was coppiced. The treatments did not significantly affect soil temperature or soil moisture measured over 0–10 cm depth. Soil respiration varied markedly during the year with high rates in spring and autumn and low rates in summer, coinciding with summer drought, and in winter, with the lowest temperatures. Very high respiration rates, however, were observed during the summer immediately after rainfall events. The mean annual rate of soil respiration was 2.9 µ mol m^?2 s^?1, ranging from 1.35 to 7.03 µmol m^?2 s^?1. Soil respiration was highly correlated with temperature during winter and during spring and autumn whenever volumetric soil water content was above 20%. Below this threshold value, there was no correlation between soil respiration and soil temperature, but soil moisture was a good predictor of soil respiration. A simple empirical model that predicted soil respiration during the year, using both soil temperature and soil moisture accounted for more than 91% of the observed annual variation in soil respiration. All the components of soil respiration followed a similar seasonal trend and were affected by summer drought. The Q₁₀ value for soil respiration was 2.32, which is in agreement with other studies in forest ecosystems. However, we found a Q₁₀ value for root respiration of 2.20, which is lower than recent values reported for forest sites. The fact that the seasonal variation in root growth with temperature in Mediterranean ecosystems differs from that in temperate regions may explain this difference. In temperate regions, increases in size of root populations during the growing season, coinciding with high temperatures, may yield higher apparent Q₁₀ values than in Mediterranean regions where root growth is suppressed by summer drought. The decomposition of organic matter and belowground litter were the major components of soil respiration, accounting for almost 55% of the total soil respiration flux. This proportion is higher than has been reported for mature boreal and temperate forest and is probably the result of a short‐term C loss following recent logging at the site. The relationship proposed for soil respiration with soil temperature and soil moisture is useful for understanding and predicting potential changes in Mediterranean forest ecosystems in response to forest management and climate change.     

Population Dynamics,Reproductive Biology and Productivity of Streblospio shrubsolii (Polychaeta: Spionidae) in Different Sediments at Low Salinities in a Mediterranean Lagoon (Monolimni Lagoon,Northern Aegean)

Monthly samples of Streblospio shrubsolii were collected from February 1998 to February 1999 at both parts of Monolimni Lagoon (0.3 psu < Sal. < 6 psu). Streblospio shrubsolii displayed a life cycle of about one year. Reproductive activity occurred from February to October. The worms showed a mean of 14 or 16 gametogenic segments. Reproductive activity, growth and density increased during spring despite the low salinities (∼0.3 psu). Streblospio shrubsolii showed faster growth, larger body size during autumn–winter, more reproductive peaks, a relatively higher mean annual density, mean anual biomass (B) and annual production (P) at the innermost part of the lagoon, in organically richer very fine sand, than those at the outer part in fine sand. Mean annual density was 1,320 individuals m^–2 at the outer part and 1,745 individuals m^–2 at the innermost. Production calculated by Hynes' s method gave a B of 0.20 g DW m^–2 y^–1 and P of 0.45 g DW m^–2 y^–1 at the outer part; the respective values at the innermost part were 0.29 g DW m^–2 y^–1 and 0.61 g DW m^–2 y^–1. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phenological development of natural populations of European field pansy (Viola arvensis) in a semi‐arid Mediterranean environment

The phenological stages, dry matter allocation and relative growth rate (RGR) of natural populations of European field pansy (Viola arvensis) were studied under field conditions for 3 years. The species exhibited an annual life cycle of 78–100 calendar days, depending on the growing season. The life cycle was initiated in early spring and ended by early summer, with an average accumulation of 1100 growing degree days. The initiation of emergence occurred in early spring at a range of maximum air temperatures between 15 and 20°C, coupled with a range of minimum air temperatures between 5 and 10°C. With increasing temperatures in mid‐spring, there was a rapid transition to the reproductive stage. Time to flowering was shortened considerably in the warm growing season. After flowering, the species appeared to allocate a relatively large proportion of biomass to the reproductive parts than dry matter allocation to the vegetative parts during juvenile stages. The maximum value of RGR was observed in the vegetative stage, whereas RGR values decreased sharply with plant age. Overall, the species showed a short life cycle and a reproductive strategy that directs resources to reproductive rather than vegetative output, thus increasing the likelihood of persistence in systematically disturbed environments that are characterized by limited growth time as a result of major events in the field, such as mechanical cultivation or herbicide application.     

Annual climate in Mexican Spotted Owl habitat in the Sacramento Mountains,New Mexico: implications for responding to climate change

Global climate change presents a growing conservation threat, but our understanding of the effects of climate change remains limited for most species. We evaluated the annual climate cycle for threatened Mexican Spotted Owls (Strix occidentalis lucida) in high-elevation mixed-conifer forests in the Sacramento Mountains of New Mexico from 2005 to 2010. We used data from a network of weather stations in Mexican Spotted Owl habitat to describe annual temperature cycles, and precipitation data from a National Weather Service weather station to describe the annual precipitation cycle. We coupled these data with equations from the literature to estimate annual cycles in resting metabolic rate and evaporative water loss, and evaluated the potential effects of a warming climate on these parameters. Annual weather was characterized by cold, dry winters, warmer and dry springs, warm and wet summers, and cool and relatively wet falls. Ambient temperature never exceeded the upper critical temperature for Mexican Spotted Owls (35.2°C), but > 90% of 663,422 hourly temperature observations were below the lower critical temperature (18.2°C). Thus, heat stress was not predicted to occur, but owls likely expended energy on thermoregulation at low temperatures. Resting energy use peaked during winter (December–February) and was lowest when owls would be feeding young (May–August). In contrast, evaporative water loss peaked from June to August, when precipitation also peaked. Mexican Spotted Owls generally appeared well-adapted to the current climate cycle in our montane study area, but late winter (February–March) may be a critical period in terms of energy requirements, and late spring (April–May) may be critical in terms of water relationships. Predicted changes in temperature through 2099 would result in reductions in predicted energy use by Mexican Spotted Owls, but increases in predicted water use. Water relationships may become increasingly important for Mexican Spotted Owls in the face of climate change, especially in warmer and drier areas. In forested areas, retaining patches of older forest with high canopy cover in cool, mesic sites may provide continued benefits to Mexican Spotted Owls under climate change.