牡蛎壳粉和石灰改良酸性水稻土对磷有效性、形态和酶活性的影响

我国南方粮食主产区土壤酸化治理是提升耕地地力促进粮食增产的重要内容,目的是探究酸化土壤改良剂牡蛎壳粉和石灰对水稻土酸度、磷有效性和形态以及酶活性和相关功能基因的影响.盆栽试验设计2种改良剂的3个施用量（0.05%、0.10%和0.15%）,以水稻为试验作物.结果表明：①牡蛎壳粉和石灰均显著提高土壤pH,降低土壤交换性酸,且改良效果随着改良剂用量增加而提高,相同用量下石灰对土壤酸性的改良效果高于牡蛎壳粉;② 4种有效磷提取剂提取的土壤有效磷测定结果表明,牡蛎壳粉和石灰显著提高H₂SO₄-P、Bray-1 P和Olsen-P含量,其中Olsen-P含量随改良剂用量的增加而提高.③土壤中不同形态无机磷含量表现为：Fe-P>Al-P>Ca-P,石灰和牡蛎壳粉显著提高Al-P和Fe-P含量,分别提高26.3%~37.4%和7.9%~23.7%;0.15%改良剂显著增加Ca-P含量;④石灰和牡蛎壳粉对土壤DHA、ALP、IPP活性和phoD基因拷贝数具有提高作用,而对土壤ACP活性、phoC和pqqC拷贝数表现为降低;⑤改良剂（0.10%和0.15%）显著提高水稻产量,0.15%用量的石灰和牡蛎壳粉分别提高水稻产量34.2%和46.8%,但对秸秆生物量无显著影响.相关分析表明,土壤无机磷和有效磷含量与pH和ALP活性呈显著正相关,改良剂通过消除土壤酸化和提高土壤磷酸酶活性来改善土壤磷营养状况,这对促进作物产量具有积极作用.     

巢湖沉积物有效磷的原位高分辨分析研究

将两种原位被动采样技术——高分辨平衡式间隙水(HR-Peeper)与氧化锆薄膜梯度扩散技术(Zr-oxide DGT)相结合,分别对巢湖西半湖7个点位溶解态反应性磷(cPW)和有效磷(cDGT)进行原位测定分析,cPW和cDGT在大部分沉积物剖面的分布相似或局部相似,说明不同深度沉积物固相有效磷组分对间隙水SRP的缓冲能力较接近.利用界面扩散通量和cDGT/cPW比值(R)表征沉积物磷的活性,从巢湖湖心向南淝河入湖口方向,界面以下6 mm的cPW、cDGT和扩散通量的变化基本一致,均呈递增趋势,表明沉积物磷的污染水平在增加;R值变化较小,说明沉积物界面处的缓冲能力差异不明显.     

有机物料与~(32)P标记过磷酸钙混合施用对磷有效性的影响

本试验利用~(32)P示踪法研究赤红壤上两种有机物料与过磷酸钙混合施用对磷有效性的影响。盆栽试验表明,纸厂废料蔗渣或猪粪与磷肥混合施用比磷肥单独施用更有利于提高格拉姆柱花草的含磷量和总吸磷量。单位施磷量引起的土壤有效磷和植株吸磷量的增加量也是有机物料单施或与磷肥混施高于磷肥单施。在前39d,~(32)P标记过磷酸钙的利用率在单独施用时为2.14％,比混合施用高一倍左右;在80d时,混合施用的磷利用率较快提高,蔗渣与磷肥混施处理超过单独施用,达22.88％。     

Asexuals looking for sex: conflict between species and mate-quality recognition in sailfin mollies (Poecilia latipinna)

When two closely related species are sympatric the process of species recognition (identifying conspecifics) and mate-quality recognition (increased fitness benefits) can yield a conflict when heterospecifics resemble high-quality conspecifics. Conflict in species versus mate-quality recognition may serve as a possible mechanism for the persistence of unisexual, gynogenetic Amazon mollies (Poecilia formosa). Amazon mollies require sperm from closely related species (e.g., sailfin mollies, P. latipinna) to start embryogenesis but inheritance is strictly maternal. When choosing mates, male sailfin mollies from populations sympatric with Amazon mollies may rely on traits indicating species identity rather than those indicating mate quality. Conversely, males from allopatric populations may rely more on traits indicating mate quality. Previous work has found that male sailfin mollies in sympatry exhibit a significantly greater mating preference for female sailfin mollies over Amazon mollies compared to males in allopatry. In addition, male sailfin mollies prefer to associate with and produce more sperm in the presence of larger conspecific females, which are more fecund. We hypothesized that male sailfin mollies experience a conflict in species recognition and mate-quality recognition in the presence of Amazon mollies that are relatively larger than female sailfin mollies. To test this hypothesis, we paired males from sympatric and allopatric populations with a larger Amazon molly and a smaller female sailfin molly. We scored the number of mating attempts that males directed to conspecific and heterospecific females. Males in most sympatric and allopatric populations demonstrate no clear preference for conspecifics. In addition, we found some evidence for a difference in mating preference between allopatric and sympatric populations with males from allopatry showing a greater heterospecific mate preference. These results indicate a conflict between species and mate-quality recognition. In sympatry this conflict may contribute to the persistence of gynogenetic Amazon mollies.     

Long-term mate and territory fidelity in neotropical buff-breasted wrens (Thryothorus leucotis)

Among sedentary species, mate and site fidelity may be imposed by year-round territoriality and high annual survivorship, both of which theoretically lead to few opportunities to move between mates and breeding territories. We examined mate and territory fidelity in sedentary neotropical buff-breasted wrens (Thryothorus leucotis) in relation to the opportunities to divorce (vacancies on neighbouring territories), breeding experience and site of origin (within vs outside local breeding population). Overall, buff-breasted wrens showed high rates of mate and territory fidelity between years, with individuals significantly more faithful to their territories than to their partners. Mate and territory fidelity was not forced upon buff-breasted wrens, as most individuals had opportunities to switch mates and territories. However, this was not uniform among all individuals. Individuals that had bred together displayed 100% mate and territory fidelity despite the fact that males and females in almost all experienced pairs had opportunities to switch mates and territories. Local recruits (philopatric offspring that acquired territories in the local breeding population) also displayed mate and territory fidelity, but fidelity occurred because recruits rarely had the opportunity to divorce prior to initiating their first breeding attempt. By contrast, almost half of all territorial individuals that originated outside the local breeding population (immigrants) had opportunity to divorce, with approximately two thirds of them switching mates and territories. Divorces occurred within the first 5 months of pairing, suggesting that immigrants may have sampled mates and territories before forming permanent partnerships.     

Why do female pied flycatchers mate with already mated males: deception or restricted mate sampling?

The polygyny threshold model suggests that females make an optimal choice between mated and unmated males. However; in birds in which males provide parental care, the fitness of secondary females is often lower than expected from this model. This has been explained by the deception hypothesis, which states that males hide their mating status and deceive females into polygyny. Yet there is no direct evidence that secondary females are unaware of male mating status when they settle. Alternatively, females settle with mated males as a result of mate competition and costs of searching. We used videofilming at nestboxes defended by males to study mate sampling of female pied flycatchers Ficedula hypoleuca. The females visited on average only 2.74 males (range 1–8, n = 43). Most (16 of 19) of the polygynous matings occurred because females had only visited mated males, or the unmated males visited became occupied by competitors during the sampling period. Among females that could choose between both mated and unmated males, the majority (13 of 16) settled with unmated males. These results lend little support to the deception hypothesis but are consistent with the view that females are able to detect male mating status but sometimes settle with mated males because of cost of searching. Prospecting females seemed willing and able to suffer the cost of fighting with aggressive primary females in the males' secondary territory if no alternative mating options were available. In addition to male mating status, females took male quality (plumage colour, age) into account in mate choice but the former appeared to be the more important. Correspondence to: T. Slagsvold     

The cause of size-assortative mating in the leaf beetle Trirhabda canadensis (Coleoptera : Chrysomelidae)

Summary Examples of positive assortative mating by body size are abundant but its causes remain controversial. I show that size-assortative mating occurs in the chrysomelid beetle Trirhabda canadensis and I test a series of alternative hypotheses to explain how this mating pattern comes about. Results suggest that assortative mating in this beetle is due to the greater ease with which size-matched pairs can achieve intromission, and not due to size-biased skews in the availability of mates or mate choice favoring large individuals. There was no correlation between male and female elytron length (a measure of body size) at the initiation of courtship, but pairs assorted positively by size at the onset of intromission. Moreover, in the laboratory, there was a negative correlation between male and female size for pairs engaged in courtship that terminated without mating. Assortative mating was not associated with a large-male mating advantage and there was no evidence of female choice of large males. Nor was there unequivocal evidence for male choice of large females; although mating females were slightly larger and considerably heavier than solitary females, males did not differ in the frequency with which they rejected large and small females. Assortative mating in T. canadensis appeared to be caused by the lower ability of mismatched pairs to achieve intromission after an encounter, both when males were larger and when they were smaller than the female.     

Delayed maturation in plumage colour: Evidence for the female-mimicry hypothesis in the kestrel

Summary In many sexually dichromatic species, young males have female-like plumage during their first potential breeding year. The female-mimicry hypothesis (FMH) supposes that by possessing female-like plumage young males deceive older conspicuous males into believing that they are females, thus reducing competition from adult males. The status-signalling hypothesis (SSH) supposes that adult males can distinguish sex, but postulates that young males reduce competition from adult males by reliably signaling low status with their dull plumage. We tested these hypotheses in the European kestrel (Falco tinnunculus). Female-like young males settled to breed closer to adult males than did other adult males (Figs. 1a, b). By settling near adult males, young males seemed to increase their chance of mating with adult females. Adult female-young male pairs had better reproductive success than yearling-yearling pairs. These results suggest that there is an adaptive value in possessing a female-like plumage colour in the breeding season. To test the FMH, we measured sexual preference of adult males when adult females and young males were simultaneously shown in an aviary. Adult males were unable to recognize sex, because in half the cases they preferred young males (Fig. 3). However, when adult males and females were shown simultaneously, males preferred females (Fig. 2). Our results support the FMH rather than the SSH, because young males successfully deceived older males by their plumage.     

Male mating speed promote hybridization in the Rana lessonae–Rana esculenta waterfrog system

Hybridization is a widespread phenomenon in many vertebrate groups. Prezygotic isolating mechanisms, probably caused by selection against hybrids with reduced fitness, reduce the likelihood of such events. Although hybrid-reduced fitness relatively to parental species is common, hybridization can also be beneficial, and hybrids sometimes outperform the pure species type. In this study, we examined two potential processes, Hubbs’s principle and male–male competition, which could enhance hybridization in the waterfrog complex and thus explain the proportion of heterospecific pairs collected in a natural pond. Firstly, by collecting 791 frogs in the field to study pair and chorus composition, we showed that in a mixed Rana lessonae–Rana esculenta population, the scarcity of hybrid R. esculenta males did not account for the proportion of heterospecific pairs: indeed, when examining pairing composition in six different choruses, we found that hybrid males were always under-represented and that R. esculenta females were found paired with R. lessonae males. Secondly, we investigated experimentally whether or nor male–male competition mechanism could explain pair formation in waterfrogs. Our mating speed experiment highlights mechanisms that could explain heterospecific pairs in a context of promiscuous mating where scramble competition was intense. To measure the rapidity with which a male grasps a female, we placed males in a grid cage with a female, and the dynamics of pair formation was monitored. R. esculenta males showed a lower pairing success than R. lessonae males as a smaller proportion of them amplexed females, and more time was needed for them to get amplexed. Thus, a less adaptative mechanism than female mate choice may also explain the mating pattern observed in waterfrog species.