R-YP1337 (Y-DNA)

YFull’s haplotree shows that the rare YP1337 lineage diverged from its brother (the more common R-YP256) about 2500 years ago; but R-YP1337 began to expand only 1750 years ago, so for 750 years it was barely surviving. However, at that point (1750 years ago), it suddenly expanded across Central-Eastern Europe, from Hungary to Lithuania and from the Czech Republic to Russia.

The early YP1337 members have likely constituted a significant fraction among the Wislans (but also among many other West Slavic, East Slavic and even South Slavic tribes) As for your clade YP1337, this is one of the two major subclades under the so-called "West Slavic" clade L260 within the large "Slavic" branch M458. Both YP1337 and its more frequent brother clade YP256 are found among the Western, Eastern and Southern Slaves, which indicates their original presence among the so-called Proto-Slavs. It is worth noting that the YP1337/YP256 ratio varies among the Slavic-speaking populations, but although such relative frequency of YP1337 (in relation to YP256, or to total L260) seems to be much higher among the Southern Slavs and probably the lowest among the Western Slavs, this does not necessarily mean that the same applies to "absolute" frequencies of YP1337 (as both L260 and YP256 show definitely the highest frequency among the Western Slavs and the lowest frequency among the Southern Slavs, while we don't have enough data to estimate the frequency of the much less common subclade YP1337 the same way).

It most likely that L260, including both YP256 and YP1337, were born somewhere in a region encompassing North-Western Ukraine and the neighbouring territories of Belarus and Poland, thus in a region roughly overlapping with the hypothetical Proto-Slavic homeland (according to the most commonly accepted Ukrainian-Belarusian hypothesis). It seems also that the majority of the early L260 members (including most of the early YP256 members and a significant fraction of YP1337) were involved in the very successful westward migration of the Early Slavs (into the partially depopulated territory, so they constitute about 15% of all males among the modern Western Slavs), while the remaining early L260 members (showing the more balanced YP1337/YP256 ratio) were a small minority component among the Early Slaves migrating east (3-4% among the modern Eastern Slavs) or south (about 1% among the modern Southern Slavs). All above is very speculative, and we need much more data about the phylogenetic structure of YP1337 and about the geographic distribution of particular subclades before being able to reconstruct the migrations of ancient YP1337 members with enough confidence. Unfortunately, the Early Slavs either cremated their deads or used a burial rite that left no archaeologically detectable traces, so the chances for any ancient DNA results helping us answer this question are relatively low