柄锈菌属中国种补充记载

本文报告了柄锈菌属4个中国新记录。它们是羊角芹柄锈菌Pucciniaaegopodii（Strauss）Roehl．多夫勒柄锈菌PucciniadovrensisBlytt、大谷柄锈菌PucciniaotanianaHirats．和艾菊柄锈菌狭叶青蒿变种PucciniatanacetiDC．var．dracunculina（Fahrend）Cummins。形态特征描述是基于中国的材料。附有简要讨论和线条图。     

Do host alternating aphids know which plant they are on?

Abstract.

• 1 To determine whether an aphid is ‘aware’ of which plant it is on, clones of a host alternating aphid, Cavariella aegopodii Scop., reared on its primary (Salix) or secondary (Daucus) host, were subjected to autumnal conditions.
• 2 Old clones produced males and egg laying females when exposed to autumnal conditions on the primary host but autumnal migrants and males when on the secondary host.
• 3 Unlike some other host alternating aphids, Cavariella did not have to spend a period on the secondary host or go through the spring migrant stage before producing sexuals.
• 4 The adaptive significance of a host alternating aphid being ‘aware’ of which host plant it is on is discussed in the light of these results.

     

Resource tracking in aphids: programmed reproductive strategies anticipate seasonal trends in habitat quality

Most aphids show cyclical parthenogenesis, have short generation times and complete several generations each season. Two hypotheses have been proposed to account for the adaptive seasonal trends observed in the reproductive strategies of aphids. Firstly, individuals of each generation modify their reproductive strategy in direct response to the conditions they experience during their development. Secondly, the reproductive strategies of the different generations are to a large extent programmed and anticipate seasonal trends in habitat quality. These hypotheses were tested by rearing individuals of three generations of the host-alternating willow-carrot aphid, Cavariella aegopodii, on both willow and carrot. This revealed that the way this aphid allocates resources to gonads and lipid reserves is independent of an aphid's weight and the host plant on which it is reared. In addition each generation shows a specific relationship between offspring size and adult size, which tends to keep the absolute investment in individual offspring relatively constant from generation to generation, inspite of the big differences in adult size between generations. That is, through programmed allometric engineering aphids anticipate the predictable seasonal trends in habitat quality and so more closely track their resources, investing relatively more in gonads when food quality is high and relatively more in lipoidal reserves when food quality is poor. Received: 25 August 1997 / Accepted: 19 October 1997     

Effect of mixed cropping on some insect pests of carrots and onions

Mixed cropping carrots with onions reduced attacks by carrot fly,Psila rosae Fab., on carrots andThrips tabaci Lind. on onions, compared with those on carrots and onions inmonoculture. Increased plant density also reduced the numbers of carrot-willow aphid,Cavariella aegopodii Scop., Carabid and staphylinid predators ofP. rosae eggs were trapped in higher numbers on the intercropped plots with higher onion:carrot plant density ratios (PDR) over bothP. rosae generations but losses of exposed markedP. rosae eggs were not consistent with these differences. In addition, the PDR treatment effect was greatest when the carrots were intercropped with young onions and virtually ineffective once the onions began to bulb.Over 90% of adultP. rosae trapped entering carrot plots were female and the majority approached the plots upwind at a height of <40 cm above the ground possibly in response to the carrot odour. Row-intercropping with onions caused fewer flies to enter the plots. Mixed cropping of carrots with onions probably reducedP. rosae attack by the onion volatiles disturbing host-plant finding particularly when the onions were young. Mixed cropping with the French marigold,Tagetes patula L. was ineffective. C. aegopodii was not directly affected by intercropping as wasT. tabaci, the latter being reduced in numbers by increased PDR possibly due to reduced apparancy of the onion plants.

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Effet de l'association culturale sur quelques insectes attaquant carottes et oignons

Résumé L'association culturale des carrottes et des oignons réduit les attaques dePsila rosae Fab sur carottes et deThrips tabaci Lind sur oignons, par rapport aux monocultures. L'accroissement de la densité végétale réduit de même le nombre de pucerons de la carotte,Cavariella aegopodii Scop. Les carabes et staphylins prédateurs d'oeufs dePsila rosae sont piégés en plus grand nombre en culture alternée avec une densité élevée (PDR) d'oignons et de carottes, pendant les 2 générations deP. rosae; mais les pertes d'oeufs marqués exposés deP. rosae ne confirment pas ces différences. De plus, l'effet du PDR est plus important quand les carottes alternent avec de jeunes oignons et virtuellement sans effet quand les bulbes des oignons commencent à se former. Plus de 90% des adultes deP. rosae piégés en entrant dans les parcelles de carottes étaient des femelles, et la majorité se dirigeait face au vent à moins de 40 cm au dessus du sol, vraisemblablement en réponse à l'odeur de carotte. L'alternance avec des rangs d'oignons limite le nombre de mouches pénétrant dans les parcelles. L'association de carottes et d'oignons a réduit probablement les attaques deP. rosae par l'action de substances volatiles des oignons, en perturbant la découverte de la plante hôte, particulièrement quand les oignons étaient jeunes. L'association avecTagetes patula L. n'a pas eu d'effet. C. aegopodii n'a pas été directement affecté par l'association comme l'étaitT. tabaci, l'effectif de ce dernier ayant pu être limité par un PDR élevé qui aurait réduit l'individualisation des pieds d'oignons.

     

Elevated temperatures alter an ant‐aphid mutualism

Ant‐hemipteran mutualisms are keystone interactions that can be variously affected by warming: these mutualisms can be strengthened or weakened, or the species can transition to new mutualist partners. We examined the effects of elevated temperatures on an ant‐aphid mutualism in the subalpine zone of the Rocky Mountains in Colorado, USA. In this system, inflorescences of the host plant, Ligusticum porteri Coult. & Rose (Apiaceae), are colonized by the ant‐tended aphid Aphis asclepiadis Fitch or less frequently by the non‐ant tended aphid Cavariella aegopodii (Scopoli) (both Hemiptera: Aphididae). Using an 8‐year observational study, we tested for two key mechanisms by which ant‐hemipteran mutualisms may be altered by climate change: shifts in species identity and phenological mismatch. Whereas the aphid species colonizing the host plant is not changing in response to year‐to‐year variation in temperature, we found evidence that a phenological mismatch between ants and aphids could occur. In warmer years, colonization of host plant inflorescences by ants is decreased, whereas for A. asclepiadis aphids, host plant colonization is mostly responsive to date of snowmelt. We also experimentally established A. asclepiadis colonies on replicate host plants at ambient and elevated temperatures. Ant abundance did not differ between aphid colonies at ambient vs. elevated temperatures, but ants were less likely to engage in tending behaviors on aphid colonies at elevated temperatures. Sugar composition of aphid honeydew was also altered by experimental warming. Despite reduced tending by ants, aphid colonies at elevated temperatures had fewer intraguild predators. Altogether, our results suggest that higher temperatures may disrupt this ant‐aphid mutualism through both phenological mismatch and by altering benefits exchanged in the interaction.