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This study investigated the tackling ability of junior elite and subelite rugby league players, and determined the relationship between selected physiological and anthropometric characteristics and tackling ability in these athletes. Twenty-eight junior elite (mean + and 13 junior subelite (mean [+ or -] SD age, 15.9 [+ or -] 0.6 years) rugby league players underwent a standardized 1-on-1 tackling drill in a 10-m grid. Video footage was taken from the rear, side, and front of the defending player. Tackling proficiency was assessed using standardized technical criteria. In addition, all players underwent measurements of standard anthropometry (stature, body mass, and sum of 7 skinfolds), acceleration (10-m sprint), change of direction speed (505 test), and lower body muscular power (vertical jump). Junior elite players had significantly greater (p < 0.05) tackling proficiency than junior subelite players (65.7 [+ or -] 12.5 vs. 54.3 [+ or -] 16.8%). Junior elite players tended to be taller, heavier, leaner, and have greater acceleration, change of direction speed, and muscular power, than the junior subelite players. The strongest individual correlates of tackling ability were acceleration (r = 0.60, p < 0.001) and lower body muscular power (r = 0.38, p < 0.05). When multiple linear regression analysis was performed to determine which of the physiological and anthropometric characteristics predicted tackling ability, fast acceleration was the only variable that contributed significantly ([r.sup.2] = 0.24, p < 0.01) to the predictive model. These findings demonstrate that fast acceleration, and to a lesser extent, lower body muscular power contribute to effective tackling ability in junior rugby league players. From a practical perspective, strength and conditioning coaches should emphasize the development of acceleration and lower body muscular power qualities to improve tackling ability in junior rugby league players. KEY WORDS skill, physique, defense, fitness, correlation

This study investigated the physiological and skill demands of 'on-side' and 'off-side' games in elite rugby league players. Sixteen male rugby league players participated in 'on-side' and 'off-side' games. Both small-sided games were played in a 40- x 40-m playing area. The 'off-side' game permitted players to have 3 'plays' while in possession of the ball. Players were permitted to pass backward or forward (to an 'off-side' player). The 'on-side' game also permitted players to have 3 'plays' while in possession of the ball. However, players were only permitted to pass backward to players in an 'on-side' position. Heart rate and movement patterns (via global positioning system) were recorded continuously throughout both games. Data were collected on the distance covered, number of high-acceleration and velocity efforts, and recovery between efforts. Video footage was also taken to track the performance of the players. to have inspection of the footage was undertaken to count the number of possessions and the number and quality of disposals. In comparison to 'on-side' games, 'off-side' games had a greater number of involvements ('touches'), passes, and effective passes. However, the cognitive demands of 'on-side' games were greater than 'off-side' games. 'Off-side' games resulted in a greater total distance covered, greater distance covered in mild and moderate accelerations, and greater distance covered in low, moderate, and high-velocity efforts. There were also a greater number of short duration recovery periods between efforts in 'off-side' games. The results of this study demonstrate that 'off-side' games provide greater physiological and skill demands than 'on-side' games. 'Off-side' games may provide a practical alternative to 'on-side' games for the development of skill and fitness in elite rugby league players. KEY WORDS game-based training, small-sided games, fitness; skill, rugby

Research into rugby league has found a significant, positive relationship between training load and injury rates. However, there has been limited research investigating this relationship in the preseason period, and the relationship between training load, and injury among professional rugby league players is yet to be examined. The primary aim of this study was to examine the relationships between training load, various psychological data, and the incidence of injury during preseason training at a professional rugby league club. Thirty-six male professional rugby league players undertook a 14-week training program. Each player's training time, intensity rating, and injury status were recorded after each training session. In addition, players rated their sleep, food, energy, mood, and stress on a scale of 1-10 (with 1 being extremely poor and 10 being excellent) biweekly. Over the entire preseason period, a total of 2,877.9 training hours were recorded for the players, with an overall incidence of injury of 6.9 per 1,000 training hours. Higher training loads during the first half of the preseason corresponded to a higher injury rate in comparison to the second half of the preseason. No significant relationship was found between the preseason weekly injury rate and the weekly load, nor was there a relationship between injury and psychological data. These findings suggest no relationship between training load, psychological data, and injury incidence during the preseason training period in professional rugby league players. However, results suggest that players may have an increased risk of injury during the early preseason period. The findings of this study may be particularly useful in professional rugby league teams to determine when a player is at increased risk of injury, using their training loads and psychological data. KEY WORDS team sport, football, collision sport, training, performance

Alternative models of community assembly emphasize regional, stochastic, dispersal-based processes or local, deterministic, niche-based processes. Community ecology's historical focus on local processes implicitly assumes that local processes surpass regional processes over time or across space to derive nonrandom metacommunity structure (i.e., a quorum effect). Quorum effects are expected late in succession among nearby sites, whereas quorum effects are not expected early in succession among distant sites. I conducted a metaanalysis of zooplankton data sets encompassing time scales of one to thousands of years and spatial scales of < 1 m to thousands of kilometers. Species co-occurrence analyses statistically evaluated presence/absence patterns relative to random patterns obtained with Monte Carlo null models. A series of weighted analyses was conducted and alternative randomization algorithms and null models were evaluated. Most zooplankton metacommunities were randomly structured in unweighted analyses, and the distribution of significant structure did not follow quorum effect predictions. Weighted analyses (e.g., by habitat area) revealed significant, nonrandom structure in most zooplankton metacommunities, but the distribution of significant structure still did not adhere well to quorum effect predictions. Finally, additional weighting for study scale (number of sites) nullified most significant area-weighted structure, and again, the distribution of significant structure did not follow quorum effect predictions. Overall, a quorum effect was not supported, perhaps related to zooplankton life histories and energetics and/or the quorum effect itself. Results at the presence/absence level of resolution indicated that local processes did not generally override regional processes over time or across space to drive community structure. A full integration of dispersal- and niche-based concepts in metacommunity dynamics will be most fruitful for unraveling community assembly. Species co-occurrence analyses were scale dependent (habitat area and study size). Future analyses should use weights for important factors (e.g., habitat area), and meta-analyses should include study scale as an additional factor contributing to apparent patterns. Key words: community assembly; local scale; meta-analysis; regional scale; succession; zooplankton.

The purpose of the present study was to examine the influence of 3 different high-intensity interval training regimens on the first and second ventilatory thresholds (V[T.sub.1] and V[T.sub.2]), anaerobic capacity (ANC), and plasma volume (PV) in well-trained endurance cyclists. Before and after 2 and 4 weeks of training, 38 well-trained cyclists ([Vo.sub.2]peak = 64.5 [+ or -] 5.2 ml*[kg.sup.-1*[min.sup.-1]) performed (a) a progressive cycle test to measure [Vo.sub.2]peak, peak power output (PPO), V[T.sub.1], and V[T.sub.2]; (b) a time to exhaustion test ([T.sub.max]) at their [Vo.sub.2]peak power output ([P.sub.max]); and (c) a 40-km time-trial (T[T.sub.40]). Subjects were assigned to 1 of 4 training groups (group 1: n = 8, 8 x 60% [T.sub.max] at [P.sub..max] 1:2 work-recovery ratio; group 2: n - 9, 8 x 60% [T.sub.max] at [P.sub.max], recovery at 65% maximum heart rate; group 3: n = 10, 12 x 30 seconds at 175% PPO, 4.5-minute recovery; control group: n = 11). The T[T.sub.40] performance, [Vo.sub.2]peak, V[T.sub.1], V[T.sub.2], and ANC were all significantly increased in groups 1, 2, and 3 (p < 0.05) but not in the control group. However, PV did not change in response to the 4-week training program. Changes in T[T.sub.40] performance were modestly related to the changes in [Vo.sub.2]peak, V[T.sub.1], V[T.sub.2], and ANC (r = 0.41, 0.34, 0.42, and 0.40, respectively; all p < 0.05). In conclusion, the improvements in T[T.sub.40] performance were related to significant increases in [Vo.sub.2]peak, V[T.sub.1], V[T.sub.2], and ANC but were not accompanied by significant changes in PV. Thus, peripheral adaptations rather than central adaptations are likely responsible for the improved performances witnessed in well-trained endurance athletes following various forms of high-intensity interval training programs. Key Words. ventilatory threshold, anaerobic capacity, plasma volume, endurance performance, short-term training

McCune and Allen (1985) asked the question 'Will similar forests develop on similar sites?' and concluded that dissimilar old-growth forests had developed on similar sites due to historical factors (colonization, disturbance, etc.). We asked 'Do similar zooplankton communities develop in similar ponds?' We compared zooplankton community structure and function in 12 newly constructed experimental ponds during 1 yr of natural colonization and analyzed a suite of physical-chemical variables to evaluate the assumption of environmental similarity among ponds. Ponds were similar for the measured environmental variables. However, zooplankton communities were structurally different, as indicated by analyses of species presence/absence, colonization and species accrual curves, and taxa (rotifer, copepod, cladoceran, and Chaoborus) density and biomass. Species varied widely in their colonization abilities. Zooplankton communities also differed in productivity of some taxa and community-level respiration rates. Scale was important in detecting structure and function differences among zooplankton communities. Species- and taxa-level analyses showed clear differences among communities, but community-level analyses of structure (species richness, total density and biomass) and function (productivity, respiration, and ammonia regeneration rates) could not identify distinct sets of communities. Community structure and function may be comparable in sensitivity for detecting change but need to be compared at equivalent scales. Dispersal (as evidenced by colonization history) was a regulator of new zooplankton communities, because it did not occur rapidly or uniformly among similar ponds. All zooplankton do not disperse readily. The extent to which dispersal limits older zooplankton communities is unknown, but genetic studies indicate low dispersal rates among established populations. Dispersal also regulates assemblages of organisms expected to be less vagile than zooplankton and in various ecosystems, indicating that 'supply-side' and metapopulation concepts are valuable for community ecology. Priority effects may have lasting influence on subsequent community structure, depending on colonization rates and sequences. We propose explicit recognition (and careful examination) of a commonly assumed but rarely tested 'quorum effect': local abiotic and biotic processes regulate communities and arrival processes do not, because potential members have already arrived. Given either priority or quorum effects, dispersal may be an important, often-overlooked process regulating community structure and function, especially when it is not rapid. Key words: colonization history; community composition and assembly; community structure; dispersal; experimental ponds; quorum and priority effects; rotifers; scale effects; zooplankton., INTRODUCTION Do similar communities develop in similar sites? McCune and Allen (1985) asked this question about established, old-growth forests, and concluded that historical factors during early succession had been important [...]

The cells of two bacterial spacecraft contaminants, Escherichia coli and Serratia liquefaciens in liquid medium were evaluated for 7 days under low temperatures with increasing concentrations of three salts to gain insight into their growth and survival under simulated Mars conditions. The reduced survival and failure of E. coli cell density to increase under simulated Mars conditions indicated that E. coli might be able to survive but not grow in surficial soils of Mars.

The Crustacean communities are studied for 3 years in a set of extant ephemeral wetlands in Illinois to examine the effects of habitat fragmentation on the genetic structure of extant crustacean metapopulations. It is concluded that the conversion of former wet prairie to agriculture may have reduced the metapopulations and that the conservation programs can preserve much of the historical biodiversity of ephemeral wetlands.